Enterprise API integration is one of the most consistently under-budgeted line items in modern software projects. This episode of DEV.co unpacks the numbers that actually appear in statements of work — not vendor slide decks — and explains why the gap between the first budget and the final invoice is almost never a surprise to engineers, even when it is to everyone else. The discussion draws on findings from MuleSoft's 2026 Connectivity Benchmark Report and Salt Security's 2024 State of API Security Report, alongside real-world project ranges compiled in this 2026 enterprise API integration cost breakdown. The episode walks through five distinct integration types and their realistic cost bands, then identifies the five technical factors most responsible for pushing a project from the low end of a range to the high end. Here's what's covered: Simple REST integrations — documented OpenAPI spec, standard auth, a few endpoints — run $8,000 to $30,000; the baseline that most projects claim to be and few actually are. Webhook-driven integrations ($20,000–$75,000) carry a small build footprint but significant operational design cost: idempotent handlers, dead-letter queues, retry logic, and signature verification all add up fast. ERP and CRM integrations with platforms like SAP, Salesforce, or NetSuite typically land between $60,000 and $250,000, with each additional orchestrated system adding $25,000–$75,000 — and weeks of waiting for sandbox access. EDI integrations run $40,000–$180,000 per trading partner, where every partner is effectively its own subproject with its own quirks and legacy expectations. Real-time event-driven architectures (Kafka, schema registries, exactly-once semantics) start at $120,000 and can exceed $500,000 — the territory of banking, logistics, and marketplace platforms. The five cost drivers explored in depth: authentication complexity, undocumented rate limit behavior, schema drift, idempotency and event ordering, and the observability infrastructure needed to operate safely in production. The episode also covers the build-vs-buy decision in concrete terms. The iPaaS market surpassed $9 billion in 2024 and is projected to reach $17 billion by 2028, and tools like MuleSoft, Workato, Boomi, and Celigo exist precisely because connector work is repetitive. But enterprise MuleSoft contracts regularly land between $250,000 and $1 million annually once non-production environments and premium connectors are factored in — and implementation services sit on top. Teams working with enterprise software development partners or evaluating API development and integration services will find the build-vs-buy framework especially useful for year-one planning. The episode closes with a practical cost template for a mid-market company integrating one ERP, one CRM, and several SaaS tools: $350,000–$900,000 for three to six integrations including platform work. For more on production-readiness concerns in complex architectures, the episode AI Agents in Production: Approvals, Audits, and RBAC Explained covers related governance and reliability territory worth pairing with this one. DEV.co RFP.co