What are the usual monthly software maintenance costs after launch?

Monthly maintenance typically comes out to that same 15-20% annual figure, split across twelve months. What that spend actually buys is uptime monitoring, a defined patch cadence, minor bug fixes, and incident response, not new feature work.

The monthly figure typically covers uptime monitoring, routine dependency and security patches on a set cadence (often weekly or biweekly, with critical security fixes applied immediately), and fixing minor bugs users report. It does not typically cover new feature development or a major redesign of existing functionality, since those add value rather than preserve what already works, and get scoped and budgeted as separate projects.

A single-service MVP with a small user base can sit at the low end of the range, since there is less surface area to patch and monitor. A product built as several services with multiple integrations needs broader monitoring coverage and more frequent dependency updates across each service, which pushes the monthly number toward the higher end of the same percentage range.

Most teams either pay for an ongoing retainer with a fixed scope of hours each month, or handle maintenance ad hoc as issues come up. A retainer is more predictable for budgeting and tends to keep patch cadence consistent even when nothing is visibly broken, while ad hoc arrangements can look cheaper in a quiet month but often cost more once something urgent needs same-week attention.