ok so this is the honest version, not the twitter success thread version.
built a plugin that auto-generates design tokens from a color palette. took 6 months evenings and weekends. launched on the figma community page and on a couple design forums.
what actually happened: week 1: 400 installs, mostly from the launch post month 1: maybe $200 from 8 people who paid for the "pro" features month 3 onward: long tail of $100-200/month without doing much 18 months in: ~$4k total
$4k over 18 months is not "quit your job" money. it's roughly $3-4/hour if you count the build time. but i also don't really do anything to maintain it and it's legitimately passive now.
the thing i'd tell myself at the start: validate the willingness-to-pay before you build the pro tier. i assumed designers would pay for tools that saved them time. most won't. the ones who will are usually agency leads or people billing clients. finding that sub-segment earlier would have changed the whole marketing strategy.