I voted for "X" and I'm going to set X=75 (Battle of Wits players are on their own). I understand no-proxy tournaments but I don't really understand "some but not all" proxy tournaments. It's kind of a bummer because I'd love to try to get a group of friends together (who no longer play competitive Magic regularly) to attend a local tournament, but it definitely isn't going to happen with the expense involved even at the fifteen-proxy level. Although maybe part of the purpose is to keep the scrubs out, in which case mission accomplished.
I think part of the rationale for partial proxy tournaments, at least historically, has been that most events are held at stores trying are trying to sell Magic cards to players. I doubt in most cases there's any "keep the scrubs out" motivation behind it.