Direct Answer
Buy off-the-shelf when (a) the workflow is standard, (b) a SaaS product has 80%+ of the features you need, and (c) integration is the biggest issue (which can usually be solved with Zapier/Make). Build custom when (a) the workflow is your competitive edge, (b) you have data flows or rules no SaaS product covers, or (c) compliance demands it.
Short version
“Buy off the shelf for standard workflows. Build custom when the workflow is your edge or no SaaS covers your data flows.”
Time-to-value matters: if a SaaS solves 80% of the problem in 2 weeks, that usually beats a 12-week custom build that solves 100%.
Run a 1-hour 'build vs buy' workshop before any custom-software discovery — it eliminates 30% of would-be projects.
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