1. Cost by scope
“API integration” covers everything from sending form leads to your email tool to building an API other companies plug into. Find the row that matches your job.
| Scope | Cost | What it covers |
|---|---|---|
| Simple integration | $750–$1,500 | One documented platform, key-based auth, data flowing one way. Example: contact-form leads into your email list. |
| Webhook receiver | $750–$1,500 | An endpoint that listens for events another service sends you (a payment cleared, a booking changed) and acts on them. |
| OAuth / two-way integration | $2,500–$5,500 | OAuth sign-in and token refresh, verified webhooks, two-way sync or routing based on responses. Example: accounting sync. |
| Multi-system integration | $7,000–$13,000 | Several services wired together, each with its own auth, events and sync rules. |
| Your own API (small) | $2,000–$4,000 | A few endpoints with key auth, OpenAPI docs and tests. |
| Your own API (full) | $10,000–$20,000 | OAuth, multiple consumers, versioning, outbound webhooks and full developer docs. |
| AI integration | $2,500–$6,000 | Your own AI provider connected to your records: summaries, drafted replies, questions answered, changes approved by your team. |
| Payment processor setup | $700–$1,200 | Connecting a processor such as Stripe to your site for checkout or invoices. |
| Booking tool connection | $200–$500 | Wiring an existing booking tool into your site’s pages, services and staff. |
| CRM / email-list connection | $200–$500 | Sending your site’s forms into the CRM or email tool you already use. |
The last three are narrower, well-worn jobs, which is why they cost less than a general integration. Booking costs have their own guide: how much a booking system costs.
2. What moves the price
Each range starts with the bare connection. These add-ons move a quote toward the top. You pick which ones you need.
| Simple integration ($750–$1,500) | Typical cost |
|---|---|
| Field mapping + data transformation | +$250 |
| Error handling + logging | +$250 |
| Scheduled sync (cron) | +$250 |
| OAuth / two-way integration ($2,500–$5,500) | Typical cost |
|---|---|
| OAuth 2.0 flow + token refresh | +$600 |
| Webhook receiver + event handling | +$900 |
| Retry logic + error handling + logging | +$600 |
| Integration test suite | +$900 |
| AI integration ($2,500–$6,000) | Typical cost |
|---|---|
| Summaries + drafted emails / replies | +$850 |
| Questions about your records (read-only) | +$1,050 |
| Suggested updates, approved by the team before save | +$700 |
| Usage limits + cost tracking | +$350 |
| Sensitive fields stripped before sending | +$275 |
| Test suite for AI output | +$275 |
How the platform authenticates
An API key is a single setting. OAuth means a sign-in flow, token storage and token refresh that has to keep working for years. That’s most of the gap between the first two rows of the table.
One way or both ways
Sending data one way is simple. Keeping two systems in sync means deciding which one wins when both change, catching duplicates and recovering from missed events.
The quality of the other side’s docs
Well-documented platforms are quick. Thin docs, missing endpoints or data that sits behind a paid tier add discovery time, which is why quotes come after the docs have been read.
3. What’s included and what’s billed separately
Included: the integration code, tested end to end, notes on how it works and where credentials live, and full ownership. Credentials sit in your own accounts. Custom APIs also ship with OpenAPI docs and automated tests.
Billed separately: anything the connected services charge for their own API or AI usage, paid to them directly. Hosting, if it runs on a managed hosting plan ($60/mo, $100/mo or $180/mo). Later changes, billed at $100/hr.
4. Zapier vs. custom: the five-year math
Zapier prices by monthly task volume, and one plan covers as many automations as fit in that volume1. A custom integration is paid once per integration and runs on your own hosting. So the answer depends on how many automations you have and how busy they are.
| Option | How it's priced | Total | Verdict |
|---|---|---|---|
| Zapier Professional, 2,000 tasks1 | $49 / mo (2,000 tasks a month, 1 user) | $2,940 | About even |
| Zapier Professional, 10,000 tasks1 | $129 / mo (10,000 tasks a month, 1 user) | $7,740 | Custom costs less |
| Zapier Team, 10,000 tasks1 | $169 / mo (10,000 tasks a month, up to 25 users) | $10,140 | Custom costs less |
| Custom integrations (ArdinGate) | $750–$1,500 each once, assumes your site already has hosting | $2,250–$4,500 | You own it |
Each plan at its cheapest published rate (usually billed annually), plus required onboarding fees. Prices checked October 2026; vendors change them, so confirm on their pricing page. Your quote is fixed after a short discovery call.
For a single integration, Zapier Professional at the 2,000-task tier totals $2,940 over five years against $750–$1,500 to build it: a custom build costs less. At three, the custom side is $2,250–$4,500, and the two come out about even. From 4 simple integrations up ($3,000–$6,000 to build), one low-volume Zapier plan costs less than building them all. If you run many small, low-volume automations, Zapier is the cheaper choice.
Volume changes that. At the 10,000-task tier, Professional totals $7,740 (three custom integrations cost less) and Team totals $10,140 (three custom integrations cost less). Custom code has no per-task fee, so busy automations, complex branching or data you’d rather not route through a third party are where it pays off. Full comparison: Zapier vs. custom integrations →
5. How quotes and timelines work
The ranges here are budgets. Your fixed quote follows a short discovery call and a read of each platform’s API docs, so missing endpoints or unusual auth are found before work starts, not halfway through.
From signed scope, a documented one-way integration usually takes one to two weeks, and OAuth, webhooks or two-way sync two to four. A small custom API takes two to three weeks; a larger one with OAuth, versioning and full tests four to six.
What to bring to the call
The apps you want connected, what should happen when (“new paid invoice → mark the job closed”), roughly how often it runs, and any Zaps you already have.
Get a number for your integration: Cost estimator →
6. Common questions
How much does it cost to connect two apps?
A documented, one-way connection with key-based auth runs $750–$1,500. If it needs OAuth sign-in, webhooks or two-way sync, it runs $2,500–$5,500. Wiring several systems together runs $7,000–$13,000. You get a fixed quote once the platforms’ API docs have been read.
Are there per-task or per-run fees with a custom integration?
Not from the integration itself. It runs on your own hosting, so a thousand runs cost the same as ten. The services you connect may still charge for their own API usage, and you pay them directly.
What does an integration cost to maintain?
Usually very little until one of the connected platforms changes its API. Fixes and changes are billed at $100/hr. Error logging (an add-on on simple integrations) is what tells you something broke before your customers do.
Can I start with Zapier and switch to custom later?
Yes, and it’s often the right order. Zapier proves which automations matter. When one gets high-volume, needs logic Zapier can’t express, or keeps breaking, that one gets rebuilt as code and the rest stay where they are.
Can AI steps be part of a custom integration?
Yes. If you already use an AI service (OpenAI, Claude, Gemini, or any provider with an API), it can be connected to your integration to summarize notes, draft emails and replies, or answer questions about your records. You keep your own account and pay the provider directly for usage, and nothing it suggests changes your data until someone on your team approves it. Adding it runs $2,500–$6,000.
Zapier is a trademark of its owner. ArdinGate isn't affiliated with it.