A lot are paying, including me for multiple projects. They have a pretty good offering. I used to use them for dev and prod, but now using neon for dev. Supabase still for prod. I had switched from mongo to supabase. I may switch to neon for prod but not in a rush.
They also offer so much more than just postgres. Though I use them only for postgres myself.
Since you use both supabase and neon, any particular strength or weakness to keep supabase for prod? I just moved my app to neon today (easy enough to test it!) and am enjoying the auto-scaling features and UI is great on neon. But I'm curious about how supabase stacks up.
Supabase feels less flexible. Also it tries to do many other things so I don't think they can focus fully on the db side. However it still works well enough for production so cannot complain too much. I haven't done benchmarks for performance latency etc though. I should!
They also offer so much more than just postgres. Though I use them only for postgres myself.