The idea is that nostr is always "pay to play".

I just listened to an older podcast by nostr:npub1l2vyh47mk2p0qlsku7hg0vn29faehy9hy34ygaclpn66ukqp3afqutajft where I think most of us builders agree. The software, in my opinion, will always be freely available (source code that is) but you will often have to pay for services. 

Most of us are just supporting nostr in our off time with spare hardware we pay out of pocket to run. Others run small businesses (like nostr.build) and need funds in order to operate. I'm pretty sure few, if any businesses are paying themselves a salary.