I know that GDKP runs are old hat to a lot of people, but I was able to participate in my first tonight. Thankfully it was spearheaded by my guild, the Danger Cart on Eldre'Thalas.
The salient point is that it was fun. I enjoyed being able to kill bosses with the potential for either loot, gold, or some combination thereof. I love the concept of GDKP runs and hope they proliferate even more in Cataclysm (although I wonder if guild experience and whatnot will impact that).
Sooooo, that said, the gold per hour is really pretty trivial. 1372g for about 2.5 hours. Again, I can't emphasize enough that the fun more than offset that, but if people get involved with a GDKP run looking to get rich, you're barking up the wrong tree.
I purchased one trinket (heroic lootship Althor's Abacus), which was probably stupid since its primary purpose for a holy paladin is pvp (which is all but dead given that arena season 8 finishes in two weeks), but all said and done I was in the red 2k for the run. Gold well spent for the amusement.
Although nobody's likely to have read this blog yet, I'll post some thoughts this weekend regarding actual AH and WoW strategies. I'm compiling a mental list, so beware!