Verified against ChatGPT · 2026-08-08
Write a business case memo that leads with the trade-off, not the pitch
Structures a business case investment memo around the real trade-off and opportunity cost up front, instead of a persuasive pitch that saves the hard part for the end.
The prompt
Ready to copy — highlighted parts are example details you can swap.
Write a business case memo for the proposed investment below, structured to lead with the actual trade-off rather than a persuasive pitch that saves the hard part for the last page. PROPOSED INVESTMENT Building an in-house customer data platform instead of continuing to pay for the current third-party analytics vendor. COST AND TIME ESTIMATE Estimated $180,000 in engineering time over 5 months, plus ongoing infrastructure cost of roughly $2,000/month. EXPECTED RETURN OR BENEFIT Eliminates the current $95,000/year vendor contract and is expected to cut data-latency issues that currently delay two downstream reporting processes by about a day each. OPPORTUNITY COST / ALTERNATIVE USE OF RESOURCES The same 5-month engineering effort could instead complete the mobile app redesign that's been queued for two quarters. KEY RISK OR ASSUMPTION Assumes the in-house platform can match the vendor's current uptime and data accuracy, which the team has never built at this scale before. Open with the trade-off itself, stated as a single direct sentence: this investment costs X and takes Y, against Z alternative use of the same resources — before any argument for why it's worth it. A reader evaluating a business case is fundamentally comparing this option against what else the resources could do, and a memo that leads with benefits and only mentions the alternative use deep in the document reads as though it's hiding the comparison rather than making it plainly. After the trade-off, state the expected return in terms that are actually comparable to the cost — same units, same timeframe where possible — rather than incommensurable language that sounds compelling but can't actually be weighed against the cost stated earlier. State the key risk or assumption honestly and specifically, including what would have to be true for the expected return to actually materialize, and do not soften a genuinely load-bearing assumption into a throwaway caveat at the bottom — if the entire case rests on one assumption holding, that assumption belongs near the top, not buried. Close with a plain recommendation and, if relevant, what the smallest reasonable version of this investment would look like as a way to test the key assumption before committing the full amount. WHAT NOT TO DO Do not open with problem-framing or context-setting before the trade-off is stated — get to it in the first sentence. Do not present the expected return with more certainty than the key risk/assumption section actually supports; the two sections need to be consistent with each other, not written as if by two different people with different levels of confidence. OUTPUT FORMAT 1. Trade-off statement (one sentence): cost/time vs. the alternative use. 2. Expected return, stated in comparable terms to the cost. 3. Key risk/assumption, stated plainly, with what would have to be true for the return to materialize. 4. Recommendation, including a smaller test-the-assumption version if one makes sense.
Customize
Optional — swap in your own details for the highlighted parts above.
Why this works
Business case memos that lead with benefits and defer the opportunity cost to a footnote read, to a sophisticated reader, as though the trade-off is being obscured rather than genuinely weighed — and since the reader's actual job is to compare this option against everything else the same resources could do, opening with the trade-off stated plainly is what respects that the comparison, not the pitch, is the real content of the decision. Requiring the expected return to be stated in units comparable to the cost — same timeframe, same kind of measure — directly targets a common weakness in AI-generated business cases, where the model will happily produce compelling but incommensurable language ('this unlocks significant strategic value') that sounds substantive but can't actually be checked against the dollar-and-time cost stated a paragraph earlier, leaving the reader to do the comparison work the memo was supposed to do for them. Insisting the key risk or assumption be stated with the same weight as the rest of the case, rather than softened into a bottom-of-page caveat, matters because a case that rests entirely on one uncertain assumption but presents that assumption as a minor footnote is functionally misleading about its own confidence level — a reader who only skims the confident-sounding return section and skips the caveat walks away with a false sense of certainty that the memo itself created by underweighting its own biggest risk. Requiring internal consistency between the confidence of the return section and the honesty of the risk section addresses a specific and common tell in AI-drafted business writing: sections generated somewhat independently can end up reading as though written by two different people with two different risk appetites, which an attentive reader notices immediately and which undermines trust in the whole document once spotted.
What you get back
Trade-off: this investment costs roughly $180,000 in engineering time over 5 months, against the alternative of finishing the mobile app redesign that's been queued for two quarters using the same team. Expected return: eliminates a $95,000/year vendor contract and is projected to cut a roughly one-day reporting delay in two downstream processes, though full payback on the $180,000 build cost takes about 22 months at current vendor pricing. Key risk: the whole case depends on the in-house platform matching the vendor's current uptime, which this team has not built at this scale before — recommend a scoped 6-week proof-of-concept on the highest-risk data pipeline before committing the full 5-month build.
Verified against
ChatGPT GPT-5.1 · 2026-08-08
Changelog
- 2026-08-08 — Initial publish, verified against ChatGPT GPT-5.1.
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