The only option I see is hosting via DBaaS with Compose or mLab or similar, and these cost $31 and $15 per month respectively for one gigabyte of data.
This seems insane to me. How can anyone afford this profitably with anything less than a total success of a side project? Surely a successful project might use hundreds or even thousands of GB of db space when people start to really use it, no? My project would involve storing thousands of PDFs, among other files.
Do people use DBaaS for such cases, or manage their own on Digital Ocean, AWS, etc? I have no knowledge of how to do that (yet).