To partly rebut what maciej is saying here, I'd point out that Backblaze is a very successful not-free service which was also courting purchase offers; paying for a service is no guarantee that you'll get to rely on that service forever, which is a major failing of web-based services in general (and a frequently-mentioned point from my clients when I suggest using some web-based service or another). But I mostly agre…
A self-sustaining product may still be sold. But if a product CAN'T sustain itself, it MUST either be sold, or shut down, eventually.