While i haven't participated in all of Duralan's games nor Bill's, I don't see any game of theirs, on my character logs at least, even with plot completion bonus that comes anywhere close to that EXP total. The closest I have is ~27000 that Sirion participated in which was 'Into the Great Unknown Pt. 8'. From memory, the only thing that may have been near or more than this was back when Ivar and Roc took out that God/Demon/Far-Realm Being.. thing.. in the desert.
Saying that just because someone recognized that you suddenly handed out a seemingly unprecedented ton of EXP, does not make your plot any less 'weighted' than anyone else's. That's just plain fabrication and the putting of words into other people's mouths. If anything you're asking to be placed on the same level as Duralan's and Bill's games, which is certainly nothing to discourage you from and you have every right to desire that same level of respect as a DM. However, you apparently valued this one game in particular at five to ten times more worthwhile in substance that any of Duralan or Bill's recent ones. So I can't really say that I can sympathize. No one is putting down your game, simply questioning your reward.
While it is true that leveling is slow, what with the past two months worth of games that I've played Syrius in just barely surpasses the amount of EXP you gave, I can't say that I could see this being any more of a big deal as any other thing we've done thus far. It's all a piece to the puzzle. Granted I'm not too excited, as a player, about essentially rushing through Ra'men's phylacteries and having to retire my level 20 character because we 'beat the game' so to say. After all I do have fun with him especially with the fairly consistent group we have of Syrius, Kami, Roc, etc.
If the EXP being handed out is indeed an issue. I might suggest picking one system that the GMs use to determine ExP gains by the players, as I believe you and Bill (and possibly Duralan) have your own chosen methods. As such, this would keep experience gains from being 'all over the map' so to speak unless the adventure really was just that easy or that hard.
If this amount of EXP is deemed to be appropriate for what has been accomplished (the slaying of a 21st of a BBEG who may just make another phylactery unless he's Voldemort), then this will become a precedent upon which such gains are appropriate. If this was to be looked at as a precedent instead of a overestimation, you would really have to ask, "What makes it worth this much if it was indeed just 1/20 phylacteries; have we not completed greater or more difficult tasks than this?"
From what I can tell just based upon the NPCs in play, it could indeed be that two level 23 Dragons, Cu-Mein, and whatever other struggles on the way was a very difficult fight, but was it actually worth that much EXP? That's what needs to be agreed upon here.