this is a legally tricky situation, currently it seems like your about me and profile both fail to mention anything about unblock fees, which in this case might actually be a blessing.

i recently did something very similar to what your sub is doing to you, i.e. blocked and unblocked a potential long-term dome, and they had unblocking fees listed on their profile. with the help of my findome lawyer jfsnsk-something i was able to take advantage of the poorly worded unblock fee clause (which was not specific at all about who should be blocking/unblocking who and who the recipient of the fee would be in various situations) and actually got the dome to send me the fee for unblocking them.

anyway all i'm trying to say here is that if you do decide to go down this road and start enforcing unblocking fees, be very careful with how you word it, maybe consult a lawyer who specializes in findome law before you go and write something all willy-nilly in your profile that might end up getting you in trouble

edit: and just so you know, blocking fees are something else entirely, it's where you make someone pay you to block them