The FAA runs the blocking programs, there's no fee https://www.fly.faa.gov/ASDI/asdi.html https://ladd.faa.gov/
A copy of the ASDI block list is on https://www.muckrock.com/foi/united-states-of-america-10/faa...
The FAA also has a new program to hand out pseudonymous aircraft identifiers via commercial providers so there probably is a fee for that https://www.faa.gov/nextgen/equipadsb/privacy/