Generally speaking, yes. Its not like most code isn't changed as a consequence of writing those tests, so the practice has immediate benefit, but future changes

Generally speaking, yes. Its not like most code isn't changed as a consequence of writing those tests, so the practice has immediate benefit, but future changes can be made swiftly and securely due to the confidence those tests should be giving you. But also your time estimate does sound wonky, 2-3x sounds extreme. Maybe you need to improve your test writing process?