An internal API costs $5,000 to $15,000, a partner or public-facing API $15,000 to $40,000, and a single third-party integration $1,500 to $8,000. Public APIs cost more because documentation, versioning, rate limiting and support tooling are requirements rather than extras.
The cost difference between an internal and a public API is not the endpoints. It is everything around them that exists because you can no longer change things quietly.
Depending on audience
Per integration
Included at delivery
Typical build
$1,500–$4,000. Resources, error shape, pagination, versioning. Cheap now, very expensive to change later.
$3,000–$20,000 depending on endpoint count and business logic behind them.
$1,500–$5,000. Keys or OAuth, scopes, per-key limits with standard headers.
$1,000–$4,000. OpenAPI specification, examples and a changelog generated from the code.
$2,000–$6,000. Signed, retried, idempotent delivery with a log your support team can inspect.
$4,000–$12,000 if integrators need self-service keys, usage visibility and onboarding.
| Type | Cost | Timeline | Why |
|---|---|---|---|
| Internal API | $5,000 – $15,000 | 3–6 weeks | You control every consumer |
| Mobile app backend | $10,000 – $25,000 | 5–10 weeks | Versioning matters, clients lag |
| Partner API | $15,000 – $30,000 | 6–10 weeks | Docs, support, stability required |
| Public API | $20,000 – $40,000 | 8–14 weeks | Portal, keys, rate limits, SLAs |
| Single integration | $1,500 – $8,000 | 1–4 weeks | Depends on the provider's API |
| Cheap integration | Expensive integration |
|---|---|
| Documented REST API with a sandbox | Undocumented or SOAP interface |
| Standard OAuth | Custom or legacy auth scheme |
| Webhooks provided | Polling required, with rate limits |
| Clear error responses | Errors returned as 200 with a body flag |
| Stable, versioned | Changes without notice |
| One-way data sync | Bidirectional with conflict resolution |
Slightly, upfront, because of schema design and resolver work. It can be cheaper over time when many different clients need different data shapes. For a public API, REST is usually the better economics due to caching and tooling.
Budget $500–$2,000 a month for a partner or public API. Consumers report issues, providers change, and versions need supporting. An internal API costs less because you control every caller.
Sometimes — via database access, scheduled file exports, or a small adapter service. We assess feasibility first and will tell you when the honest answer is that it is not practical.
Almost always the provider: undocumented behaviour, sandbox environments that differ from production, and rate limits discovered during testing. We build in a discovery step against the real API before committing to a fixed price.
Indicative ranges in USD. Every engagement is quoted to a written scope before work starts, so the number you approve is the number you pay.
$2,000 – $4,500
1–2 weeks
Best for: Getting the contract right first
$8,000 – $30,000
4–12 weeks
Best for: Partner and public APIs
$1,500 – $8,000
1–4 weeks
Best for: Connecting a third-party system
How we think about this work, in more depth.
Cost guide
A 30-minute call, then a written proposal with scope, price and timeline within two to three working days. No retainer required to get a real number, and no obligation if the answer is that we are not the right fit.