There are 86 guilds that have beaten tower. Maybe 75 of those are still active. That is probably 4000 players right there. For every person in a tower+ guild, there are at LEAST two that aren't - so that's at least 12,000 players. I would be surprised if there aren't more like at least 18,000 active subs, but can't confirm that.
Fry's number, since it's based in part off mmo subscription data I'm sure, is probably a lot closer to accurate than anyone else's guess. So, that's 1-2000 of 12-18000 players at a minimum.