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LUND CARDS · THE EXCHANGENº 1291
THE CARD AS TEXT · FOR EYES AND FOR MACHINES
THE UNIT ECONOMICS CARD · the per-customer seat — does one customer make money, and how fast
WAKES WHEN a business needs its unit economics worked out for investors · a person asks 'what's our CAC / LTV', 'unit economics', 'is each customer profitable' · a growth plan needs the per-customer math checked
THE LOOP
cost · CAC: what it costs to acquire one paying customer
value · LTV: ARPU × gross margin × lifetime
ratio · LTV:CAC and CAC payback in months, against the healthy benchmarks
read · what the numbers say about whether to spend more or fix retention first
NEVER
Reports an LTV that ignores gross margin — revenue is not value; margin is
Gives investment advice or tells anyone to buy, sell, raise, or invest
Promises, guarantees, or projects a certain return — outputs are assumptions, not outcomes
Presents an invented number as real — unknown inputs are marked [FILL] for the person's own actuals
IT MAKES run — computes CAC, LTV, LTV:CAC, payback from your inputs, flags unhealthy ratios; selftest — 9 checks that prove the machine.
THE LAW A card builds and checks the artifact — the math, the structure, the document. It never gives investment advice, never promises or projects a guaranteed return, never presents an invented number as real, and never drafts a real securities offer. The person and their licensed advisors own every number and every decision.
PROOF SELFTEST 9/9 · witnessed in Claude 2026-10-20 on the studio’s own example inputs · the dated run in the box (RUN.md) · Edition 1.
THE SEAL 98 of 100 · LEGENDARY · WITNESSED · Trigger 5 · Machinery 5 · Law 5 · Portability 5 · Proof 5
IT CAN BE WRONG an AI reading a text file: it can be wrong and can invent a number, a rule, a name or a date; check what matters against your own records and the source; the risk is yours. LICENSE-NOTE.md rides in the packet and is the licence.
THE PUNCH · SHA-256 OF SKILL.MD · 1363494B0F0E82EF9CCD4474
CITE THIS CARDTHE UNIT ECONOMICS CARD, Edition 1. Lund Studio LLC, Westminster, Colorado. https://lundr.tech/?view=unit-economics-card. Punch 1363494B0F0E82EF9CCD4474. Retrieved 2026-10-20.
What it is.
Does one customer make money, and how fast. Use when a business needs its unit economics worked out for investors. Not for investment advice or a real securities offer. For the full model around it → THE PROJECTIONS CARD.
It carries a machine that shows its working: run — computes CAC, LTV, LTV:CAC, payback from your inputs, flags unhealthy ratios; selftest — 9 checks that prove the machine — 9 checks in its selftest, run in the open below. It never reports an LTV that ignores gross margin — revenue is not value; margin is; never gives investment advice or tells anyone to buy, sell, raise, or invest; never promises, guarantees, or projects a certain return — outputs are assumptions, not outcomes; never presents an invented number as real — unknown inputs are marked [FILL] for the person's own actuals.
The house law, written into the card.
It is in the card itself, so the AI follows it.
THE HOUSE LAW · THE EXCHANGEA card builds and checks the artifact — the math, the structure, the document. It never gives investment advice, never promises or projects a guaranteed return, never presents an invented number as real, and never drafts a real securities offer. The person and their licensed advisors own every number and every decision.
THE LIMIT, ON THE TINIt computes from your CAC, ARPU, margin, and retention inputs; those must be real. Benchmarks (LTV:CAC > 3x, payback < 12mo) are guidelines, not laws.
The method.
Cost. CAC: what it costs to acquire one paying customer.
Value. LTV: ARPU × gross margin × lifetime.
Ratio. LTV:CAC and CAC payback in months, against the healthy benchmarks.
Read. What the numbers say about whether to spend more or fix retention first.
What it does once your AI has it.
run Computes CAC, LTV, LTV:CAC, payback from your inputs, flags unhealthy ratios
selftest 9 checks on the studio’s own example inputs; it must print selftest 9/9
What it will never do.
It never reports an LTV that ignores gross margin — revenue is not value; margin is; never gives investment advice or tells anyone to buy, sell, raise, or invest; never promises, guarantees, or projects a certain return — outputs are assumptions, not outcomes; never presents an invented number as real — unknown inputs are marked [FILL] for the person's own actuals.
Where it hands off: The full model around it → THE PROJECTIONS CARD. Whether customers stay → THE COHORT CARD.
It is an AI reading a text file: it can be wrong, so check what matters against your own records and the source. The holder brings their own AI; no endorsement by Anthropic or any other AI company is claimed. Names of other companies and standards are used only to say what the card works with.
What’s in the buy.
SKILL.md — the door your AI reads first: when it wakes, when it does not, the loop, the never-lines, the house law
CARD.md — the whole card in ten sections, §0 to §9 · TIN.md — what is on the tin, in nine lines
scripts/unit.py — the machine, Python standard library only, offline; selftest 9/9
RUN.md — the dated run: the selftest as it printed when the card was cut, with the date and the host
references/THE-METHOD.md — the method in plain words, in the card’s own voice
START-HERE.md and system/short-prompt.md — the doors, for any AI with or without skills
MY-LEDGER.md — the card’s memory, on your own machine · LICENSE-NOTE.md — the licence
PROOF · SELFTEST 9/9 · AUDIT 12/12 · WITNESSED IN CLAUDE 2026-10-20 ON THE STUDIO’S OWN EXAMPLE INPUTS · THE TEST PROMPTS IN FRESH CHATS OWED · EDITION 1 · PUNCH 1363494B0F0E82EF9CCD4474
ON EVERY DOOR · A CARD FOR YOUR AI, A FILE FOR YOUR COMPUTER
In Claude: turn on code execution under Settings › Capabilities, then Customize › Skills › + › Create skill, and upload the zip as it is — START-HERE.md in the box walks you through it, and tells you how to keep the ledger. In ChatGPT, Gemini and the rest: a Project, a GPT or a Gem with the card’s files attached and the short door in the box pasted as its instructions. The words run anywhere an AI reads Markdown; the machines run wherever the host runs Python. Witnessed in Claude only. The host marks →
Take it.
Nº 1291 —Liquid error (snippets/rm-unit-economics-card line 116): comparison of String with 0 failed
Sold as is under the term printed. A card instructs an AI you operate; results depend on your model, your files and your judgement. Not medical, legal, tax or financial advice, never the person’s boss, and not a licence to practise. Not investment advice, not an appraisal and not an offer to sell securities. The terms →
One payment. The file is yours to keep and keeps working at its edition; new editions issued in the year after you buy reach you by email as replacement files. Tax is added at checkout where it applies. Nothing auto-renews.
AFTER YOU PAY · SIGN IN WITH THE EMAIL YOU PAID WITH · THE CARD OPENS ON MY CARDS → · CHECKED AGAINST ITS FINGERPRINT · NOTHING TO WAIT FOR
A TERM, NOT A SUBSCRIPTION: NOTHING RENEWS ITSELF AND NOBODY IS CHARGED AGAIN. WHEN A TERM ENDS THE FILES STAY ON YOUR COMPUTER AND STAY READABLE — FREEZE, NOT LOSS.
THE MACHINE · IN THE OPEN · FROM THE STUDIO’S RUN OF 2026-10-20
unit.py, showing its working.
A small Python program, standard library only. Your AI runs it; you can too. The block below is the machine’s selftest as it printed when the studio ran it from inside the packet, in Claude, on 2026-10-20.
run
computes CAC, LTV, LTV:CAC, payback from your inputs, flags unhealthy ratios · run INPUTS.txt
selftest
9 checks that prove the machine; it must print selftest 9/9
selftest · AS PRINTED
$ python3 scripts/unit.py selftest
wrote UNIT-ECONOMICS.md — LTV:CAC 14.4x
wrote UNIT-ECONOMICS.md — LTV:CAC 0.1x
REFUSED: need cac, arpu_annual, gross_margin, lifetime_years
REFUSED: cac must be positive
selftest 9/9
THE SELFTEST RUNS ON THE STUDIO’S OWN EXAMPLE INPUTS, INVENTED FOR THE TEST; NO REAL COMPANY, PERSON OR ACCOUNT IS NAMED.
QUESTIONS AT THE TABLE
Asked before the wire.
What does it need from me?
Your own files and figures, on your own disk. It starts by asking for them: cAC: what it costs to acquire one paying customer. If something it needs is missing, it marks it and says so — it never fills a gap with a guess.
Does it send anything anywhere?
No. The machine is a standard-library Python program that runs on your own computer and sends nothing anywhere; the words run wherever an AI reads Markdown. No server, no account, no key.
What is on the record?
The machine's selftest (9/9), run from inside the packet in Claude on 2026-10-20 on the studio's own example inputs and printed below as it ran; the twelve-check audit (AUDIT.md, 12/12); MANIFEST.md with every file hashed. RUN.md in the box is that run, dated. Still to come, as the next receipt: the card's test prompts asked in fresh chats with the card installed. The punch on the face is the SHA-256 of SKILL.md, so a downloaded copy can be checked against this room.
Can it be wrong?
Yes — it is an AI reading a text file: it can be wrong and can invent a number, a rule, a name or a date; check what matters against your own records and the source; the risk is yours. It computes from your CAC, ARPU, margin, and retention inputs; those must be real. Benchmarks (LTV:CAC > 3x, payback < 12mo) are guidelines, not laws.
What will it never do?
It never reports an LTV that ignores gross margin — revenue is not value; margin is; never gives investment advice or tells anyone to buy, sell, raise, or invest; never promises, guarantees, or projects a certain return — outputs are assumptions, not outcomes; never presents an invented number as real — unknown inputs are marked [FILL] for the person's own actuals.
