Someone needs to create a site where it has a list of paid relays. I didn't even know you were operating a relay. Is that 21 sats per month? or one time payment. 
I think if there was a list more people would be using paid relays. 
Most people think joining a relay would cost a lot. At least that's the impression I got from others.  

 https://nostr.watch/relays/find 

 yes, nostr watch has a large list.  and soon we can use nip66 draft to start building a distributed database of the relays in notes so that clients wont need to call nostr watch apis. 

 Any idea why nip66 is not listed here?:
https://github.com/nostr-protocol/nips 

 its still in draft, but its the real deal.. you have to search for its PR.  (search nip66) 

 Spam ?? - it is a special service for new  comers .. reply guy tells them how far  their message reached :-)