[quickthrower2]

The thing I find blows out estimates more is complexity in the codebase.

Typescript can be learned to a sufficient level that it has zero drag and saves you time when you need to refactor or understand someone else’s code.

Webpack is a pain to learn but like git you learn it once and benefit again and again.

But codebase complexity can knock estimates for 6. Someone’s crappy spaghetti design can below those assumptions in an estimate by an order of magnitude. And it could be a detail buried somewhere that wasn’t easy to discover. Like finding asbestos in your ceiling as you are about to remodel your house. Except a lot harder to explain to management!