Build vs. buy

Master Asset & Software TCO Calculator

Score a custom build against a bought platform on fully loaded engineer-years, compliance certification, maintenance headcount and roadmap opportunity cost — then stress-test the result for sunk-cost and key-person bias.

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Decision VerdictBUY

Verdict: BUY / UPGRADE

Managed SaaS saves $668,620 by eliminating manual SOC 2 Type II audit and infrastructure engineering drag.

3-Yr Custom TCO

$681,000

3-Yr SaaS TCO

$12,380

Break-Even

4.8 Months

SaaS CPU / Mo

$0.0138/MAU

⚙️ Input parameters

Step 2 of 4

Monthly Active Users (MAUs)

25,000

Developer Loaded Rate ($/hr)

$85/hr

Initial Build Time (Months)

3 months

Maintenance Overhead FTE

50% FTE

Compliance target level

SaaS Managed Platform

3-Year SaaS Cumulative TCO

$12,380

Visible setup & integration

SDK Setup Labor$680

Subscription overage

Monthly License Fee$325 / mo

In-House Custom Build

3-Year Custom Cumulative TCO

$681,000

Upfront CapEx (Visible)

Initial Build Labor$61,200

Hidden OpEx Drag (Invisible)

3-Yr Upkeep:$244,800

3-Yr Compliance:$225,000

Opportunity Cost:$150,000

⚠️ Strategic risk assessment

Select the behavioral checkboxes to analyze risk biases:

Step 4 of 4

Sunk Cost Bias"We have already spent substantial resources and developer hours patching our custom auth logic, so we must keep maintaining it."

Key-Person Turn-Over Risk"Our custom auth middleware, OAuth flow, and token session validation were built and are maintained by a single senior engineer."

Brittle Integration Tax"We stitch multiple no-code visual tables and external databases (e.g. Notion, Zapier, Softr) to sync user sessions."

Operator notes

How to run it

1. Pick the mode that matches the decision — enterprise build-vs-buy, cost-per-use, repair-vs-replace, or the tinkering tax.
2. Load your own rate card: fully loaded engineer-year cost, compliance scope, maintenance headcount.
3. Read the visible-versus-invisible cost matrix, which is where the off-ledger costs appear.
4. Complete the bias check before circulating the result — a defensible number with an unexamined premise fails in review.

Formulas

Custom build TCO

build + 3×compliance + 36×maintenance + opportunity

Per-use asset TCO

sticker + operating + upkeep

Asset tech-debt index

age × immediate repair cost

Monthly tinkering tax

troubleshoot hours × value of time

Every calculation runs client-side and can be bookmarked or saved locally on your device.

FAQ

What makes this figure loaded rather than nominal?

The build side is priced in engineer-years at a loaded rate, not headcount months at a salary: compliance certification effort, ongoing maintenance FTE and the roadmap capacity the team gives up while it is maintaining the thing instead of shipping.

Why does the engine ask about sunk cost and key-person risk?

Those two biases are what make a build decision get re-affirmed after the arithmetic has already turned. Naming them in the model is the point — the number is only actionable if the argument around it is acknowledged.

Does it cover per-use assets as well as software?

The same normalization applies to any asset whose cost splits into a sticker price, an operating cost and an upkeep cost — which is why the engine handles both a CIAM build-versus-buy call and a cost-per-use asset decision with one method.

Related dispatch

Build vs Buy ; Professional studio product photography of a polished brass balance scale on a pristine seamless white background, one pan holding a rolled glowing blueprint and miniature gears, the other pan stacked

The $250k AI Upkeep Tax: Why Build-vs-Buy Is an Engineer-Years Decision

The enterprise build-vs-buy decision is no longer about initial sticker price—it is about the compounding, long-term cost of ownership. While rapid prototyping makes custom tools appear cheap, they carry steep financial and operational risks. The Hidden Cost of Building: A homegrown tool averages $375,000 in upfront engineering payroll before it even works, plus a permanent $125k–$250k annual maintenance bill. The Risk of Buying: Vendor pricing is highly volatile, with over 76% of SaaS buyers facing unexpected costs and rapid price shifts after signing. The Strategic Playbook: Evaluate both paths in total engineer-years, restrict internal builds strictly to core strategic advantages, and mandate a reversibility test before committing.

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