there are plenty of sites doing commemorative certificates, family heralds, tartan, all that kind of stuff. so there must be a strong market for it all, I think its very popular in america.
and along with that there are several sites which sell GRO certificates for a profit without telling the customer that they can get them direct from the GRO for cheaper. these sites have not been told to stop doing so, only to stop pretending to be "official" or connected to the GRO in some way.