SAMPLE — ILLUSTRATIVE DATAFictional company. Not a client engagement.

Decision room

Should we build our customer data platform in-house or buy one?

A $40M-revenue B2B services firm needs a customer data platform to unify records across three acquired business units. Engineering has proposed building it; a vendor has quoted for the same scope. The CFO must recommend one path to the board.

Decision owner: Chief Financial Officer
Deadline: Board meeting, 12 weeks out
At stake: ≈$1.9M of three-year spend, plus 9 months of engineering capacity
Alternatives: 3 considered

Decision brief

Buy the vendor platform. Over three years it costs $126.3K less than building, on the assumptions recorded below.

Build — 3-year total

$921.3K

Buy — 3-year total

$795.0K

Buying saves

$126.3K

The assumption this turns on

Annual maintenance is assumed at 22% of the build cost. The two paths cost the same at 14.4%. Below that, building is cheaper. That figure is an industry range rather than this team’s measured history — which makes it the first number to replace with evidence.

Change the assumption. See whether the decision changes.

This is the model a customer receives — not a screenshot of one. Move the slider and every figure on this page recalculates.

Annual maintenance, as % of build cost

Break-even at 14.4%

22%

5%40%

At 22% maintenance, buying is cheaper over three years by $126.3K.

Three cases, not one forecast

A single number hides the disagreement. These three make it explicit — and they do not all point the same way.

Quoted plan

Engineering's estimate and the vendor's signed quote, taken at face value.

Build (3 yr)$921.3K

Buy (3 yr)$795.0K

Buy cheaper by $126.3K

Build runs long

The build takes 45% longer than estimated and carries a heavier maintenance load — the most common failure mode for in-house platform work.

Build (3 yr)$1.42M

Buy (3 yr)$795.0K

Buy cheaper by $620.6K

Lean build

A smaller team ships a narrower first release on time. The optimistic case engineering is arguing for.

Build (3 yr)$483.7K

Buy (3 yr)$795.0K

Build cheaper by $311.3K

Assumption ledger

Every number carries where it came from, who owns it, when it was set, and how far we trust it. An observed fact and someone’s estimate are not the same kind of number, and a model that renders them identically cannot be challenged properly.

Assumption	Value	Type	Source	Owner	As of	Confidence
Engineers on the build Named individuals are already allocated in the capacity plan.	4 FTE	Customer assumption	Engineering capacity plan, v3	VP Engineering	2026-07-14	high
Loaded cost per engineer	$185,000	Observed fact	2026 payroll actuals plus 28% benefits and overhead load	Finance	2026-07-02	high
Months to first production release Raise confidence by benchmarking against the last two platform builds and their original estimates.	9 months	Customer assumption	Engineering estimate; not validated against a comparable delivered project	VP Engineering	2026-07-14	low
Annual maintenance, as % of build cost This is the assumption the recommendation turns on. Replace with the team's own measured run cost on an existing internal service.	22%	External estimate	Vendor-neutral industry range of 15–25%; midpoint plus 2pts for multi-unit data complexity	GradeCircle analyst	2026-07-20	medium
Vendor implementation (one-time)	$75,000	Observed fact	Signed vendor quote, valid 90 days	Procurement	2026-07-09	high
Vendor licence (annual) Pricing beyond year 3 is not fixed and is excluded from this model.	$240,000	Observed fact	Signed vendor quote, 3-year term, flat pricing	Procurement	2026-07-09	high

Which assumption actually moves the answer

Monte Carlo, 500 samples, perturbing every input within its plausible range and correlating each against the three-year cost difference. Figures shift slightly between runs — that is sampling, and we would rather show it than hide it.

Running analysis…

Risks on the record

The 9-month build estimate has not been validated against a comparable delivered project.high
Maintenance share is an industry range, not this team's measured history.high
The vendor quote is valid for 90 days; renewal terms after year 3 are not fixed.medium
Four engineers on this build are four engineers not on the product roadmap.medium

What this model excludes

Taxes, cost of capital, and discounting — figures are undiscounted pre-tax cash
Strategic option value of owning the codebase
Switching cost if the vendor is replaced in year 4+
Revenue upside from either path — this compares cost to deliver the same scope

Verification status

SampleDraftSource-verifiedAnalyst-reviewedDecision-approvedOutcome-measured

This model sits at Sample: the structure is real and the arithmetic runs live, but the figures are illustrative and no analyst has signed them off against a real company’s data. A customer engagement moves up this ladder — source-verified inputs, analyst review against a published checklist, then a named approver. Outcome-measured comes later, when actuals are compared against what the model predicted.

That was our example. What's your decision?

Yours will not look like this one — different options, different criteria, different numbers. Describe it in a sentence and we will show you the inputs we would need, the model we would build, and the timeline, before you commit to anything.