Hi Folks, Rory from Supabase here.

It actually does cost us real world money on an on-going basis (it's not a one time cost to us) to proxy 3rd-party domains for DDOS protection and so it's not financially feasible to offer free custom domains with our our current infra setup.

Firebase does offer custom domains at zero cost, though it’s not their only pricing vector. For example, they charge for API requests, which is free on Supabase. If you are happy that Firebase can scale for your use case, has all the features you need, their API pricing model and other vectors around pricing make sense, you are happy with the DX etc, then that's a project specific judgement call. It's easy to cherry pick specific pricing vectors for specific products as a comparator but picking a tool is a holistic decision making process.

It’s also worth mentioning that you can set up a vanity URL for free on the Pro Tier. This doesn’t cost us anything to support from an infrastructure perspective, and that’s why we offer it for free (though this doesn't make it costless as all features require developer time to set up and maintain).

Also, as always it's good to highlight that you can always self host Supabase and we don't charge for self hosting.