Don't think you're Google and you have money to throw away... they only do that because they do have money to throw away, but they know that this kind of expense may, in very rare cases, pay off later as they find a market worth exploring further... you don't have that luxury. Indie developers offering free services which actually cost them money only makes sense if they have proven plans to "convert" most free users to a paid plan, otherwise you're literally donating services to your "users".

Is the cost mostly bandwidth? Cloudflare free tier is a godsend for static sites. I have a project which is audio-heavy and has used 2TB of bandwith since the start of January. It would have been about $180 of egress costs from S3, but routing it through the Cloudflare free tier CDN with an agressive caching policy has basically eliminated those costs.

That's called "a good problem to have". Seek monetization, funding, scale - popularity is a difficult thing to achieve in a world of infinite choice.

Maybe your friend could ask for donations for hosting or find a relevant sponsor to sponsor hosting.

You move it to a good but affordable host like Hetzner and call it a day.