The most commonly missed one is maintenance. Software needs updates, links break, and content goes stale. A site left untouched slowly degrades in security and search performance. Plan for either time or a support arrangement to keep it healthy.
The other quiet cost is change. Businesses evolve, and the site has to keep up. A build that's cheap because it's rigid can cost more later when every small edit needs a developer. Ask how updates work before you sign.
Updated July 2026