Here is an example of a successful business bootstrapped that way: https://twitter.com/levelsio/status/1717183107529576672

Quoted here:

First version was an index.html + @Stripe link + @Typeform to upload photos, then I manually dl'd the photos and uploaded them to the GPU

Pic 2 is current version as a web app after 1Y: 100% automated, 1850 customers @ $79K MRR, renamed to http://photoai.com