I'm using Amethyst. First time I've heard of paid relays. Do you pay per post/interaction?
Discussion
Yeah a few of the big ones you have to pay for 'network time' and they will publish your notes to their relay.
If you dont pay, you can read the relay but you cant post to it. The going rate seems to be 10k sats per month. Which feels steep, but I guess given the real world energy the data servers cost, is probably fair...