Buy vs build for SaaS infrastructure
Buy-vs-build calculators price one module at a time. The real decision compounds across every module a SaaS needs, and the tipping point is not where most posts put it.
In short
Building auth and usage metering yourself runs about $162,000 in year one for one engineer, using this site's own published figures for each. A managed platform covering both is $490 a year. That gap comes from needing both modules at once, which single-module calculators never price.
Every buy-vs-build framework asks the question one module at a time. Should you build auth, or buy it? Should you build billing, or buy it? Priced separately, both questions come out close enough to argue about, which is exactly why the posts answering them read like a coin flip.
Priced together, for one team building both in the same year, they stop being close. Here is the arithmetic, using this site's own published, line-item figures for two modules rather than a new estimate invented for this post.
The question
What does it cost one team to build and maintain the infrastructure a normal B2B SaaS needs in its first year, against paying for a platform that already has it?
The assumptions
Nothing new here. These are the same inputs the auth-cost post and the metering-cost post already derived and showed their work on - reused, not re-invented, so the totals below stay traceable to arithmetic you can go re-check.
- One senior engineer, loaded at $150 an hour, building both modules in sequence rather than two engineers building them in parallel.
- Auth scope: email/password signup, sessions, password reset, one OAuth provider. No SSO, no MFA.
- Metering scope: idempotent event ingestion with correction and backfill tooling, not a single incrementing counter.
- Maintenance held at 20% of build cost every year, the same benchmark both source posts use, for patching, provider API changes and the correction bugs each domain produces on its own schedule.
- Mid-scenario build times from each source post: 4.5 weeks for auth, 4.5 months for metering.
- Buy-side price is BuildBase's own Launch plan, verified against the platform constants on 3 September 2026.
The arithmetic
| Module | DIY build (mid) | DIY maintenance, yr 1 | Year-one total |
|---|---|---|---|
| Auth | $27,000 | $5,400 | $32,400 |
| Usage metering | $108,000 | $21,600 | $129,600 |
| Combined | $135,000 | $27,000 | $162,000 |
$162,000 to build and maintain two modules, for one year, with one engineer. BuildBase's Launch plan, which covers auth and metering alongside billing and workspaces rather than either alone, is $490 a year paid annually.
That is not a fair one-line comparison and it is not meant to be read as one. $490 buys more scope than the $162,000 does - it also buys billing and workspaces, which the DIY total above does not include at all. Even granting that gap generously, doubling or tripling the managed price to account for it does not get anywhere near six figures.
The total, and what actually moves it
The $162,000 headline is not the interesting number. The interesting number is that it is not $32,400 plus $129,600 read as two separate, comparable decisions - it is one number, because one team has to carry both maintenance lines going forward, every year, on top of whatever they build next.
That's the part single-module calculators miss structurally, not by oversight. A post that prices auth alone is honest about auth and silent about the four or five other things the same SaaS still needs - billing, workspaces, notifications, feature flags. Each one adds a full year-one build plus a recurring maintenance tax, and those maintenance hours don't average out across modules. They stack, on the same one or two engineers, who also have a product to ship.
Key takeaway
Auth alone or metering alone can honestly go either way. Needing both at once, on the same team, is what turns a marginal call into a $162,000 question - and every module past the second one moves the answer further in the same direction.
That's also a different failure mode than the one the vendor-stack post covers. Buying four best-of-breed vendors instead of building avoids the $162,000, but it swaps the build-hours tax for an integration tax - four webhook formats, four auth models, four places a number can drift - that a subscription total never shows either. Building, assembling, and buying one platform are three different trades, not two.
Where this math stops applying
You only need one module, not several. Building auth alone at $21,600-$43,200 is a defensible call for plenty of teams, as the source post argues. The case for buying gets stronger with each module added to the same build, not because any one of them got more expensive, but because the team carrying the maintenance did not grow to match.
Infrastructure is your actual product. A billing or auth company is pricing this in reverse - none of it is overhead, it's the thing being sold.
Your engineer's rate sits well below $150 an hour. The gap compresses at a junior or offshore rate, though not by enough to flip a two-module build: even at $50 an hour, $162,000 becomes $54,000, still two orders of magnitude past $490.
You already have idle ops capacity. Self-hosting the same modules trades the license line for compute, a managed database and patch time, which is a different axis from this post entirely - it's managed-versus-self-hosted, not build-versus-buy, since self-hosting still means running BuildBase's modules rather than writing your own.
You're past roughly 1,000 tenants. At real scale the tenancy model itself becomes the binding cost, and the constraint shifts from engineering hours to a connection-pool ceiling that no build-cost table on this page prices in.
Where BuildBase sits in this
We didn't write this post to make the arithmetic land somewhere convenient. PlugNode, AgentCenter and Imejis - three of the six products we run ourselves - use auth and OAuth, team workspaces, Stripe billing and usage-based credit metering, the exact module set this post prices out separately, on one platform instance each rather than a separately built and maintained stack. That's less a claim about BuildBase and more a description of what not re-deriving this math five times actually looks like day to day: infrastructure work like this is estimated to eat 60-70% of engineering time on a typical SaaS team, and every module you build instead of buy is a slice of that percentage with your name on it, every year, not just at launch.