Built a vinted fee calculator, made $0, need honest feedback

so i built vinted-calc because i kept doing the math wrong when listing stuff. you paste in your asking price and it tells you exactly what you'll actually get after fees and payout minimums. takes like 30 seconds to use.

it's live and working. analytics say maybe 40 people have used it this week. revenue is zero because i haven't figured out how to monetize it without making it annoying. ads? subscription? honestly no idea.

here's what i'm stuck on: how do you actually get people to find something like this? i posted it once on r/vinted and got some traffic but nothing sustained. seo is impossible when your audience is like five thousand people max. tried twitter but my account has like 12 followers so that went nowhere.

i'm not looking for validation (though if you use it and it helps, that's cool). i want to know what founders here actually did to get their first real users. was it just grinding and posting everywhere? did you build something slightly bigger? did you find a community and actually hang out there?

and if you think the idea itself is trash, tell me that too. i'd rather know now than spend months on something nobody wants.

feel free to poke at it here if you want: https://vinted-fee-calculator-tan.vercel.app