Our workflow platform vendor hit us with an 18.3% renewal increase — $28K more overnight. We paid it (product launch in 6 weeks, no time to migrate), then ran a proper 3-year TCO analysis. The math was brutal: staying would cost $669K over three years; building internally, $370K. We executed a 14-month staged exit, came in one month early, and now save ~$180K annually. The real lessons: year-one build costs more than staying, parallel-run phases always blow the budget, and the productivity drag of a vendor you resent never shows up in anyone's spreadsheet.