There is an official Alchemy of Craft(Poison) DC for Dragon Bile. Listed in a couple of different sources now, Tome & Blood for one, I think. Sure, you may be able to butcher the dragon and remove its bile gland, but at some point you'd still have to make a DC 30 to actually get the poison.
Not to mention that crafting poisons follows the normal Craft rules, so that one dose of 1500 gp poison is going to take you... about 117 days (assuming a check result of 30, so 90 gp/week).
Yes, Craft rules are rather wacky that way, but them's the rules.
With "hacked it up and spoiled it" I meant you had to cut open the dragon to get to the bile gland (aka gall bladder, I guess). Since presumably none of you have any skills in disecting magical creatures, you probably cut into a bunch of other stuff that could have made very valuable components. Did any of you even know what a bile gland looks like, or where to find it? That dragon corpse, in good condition (granted, you had to kill it first...) could easily be worth tens or hundreds of thousands of dollars in spell components etc. The fact that you've hacked it apart to get at some 1500 gp poison could easily have reduced the price you can get for it by much more than the price of the dragon bile.
Of course, your DM could decide that a dragon corpse is essentially worthless, except for its hide and bile gland. But it's a friggin dragon! Just think of how many species of tigers and rhinos are being driven to extinction just because people in China believe their bones have magical healing properties. Don't you think in a magical world that would be even more true?
Forget about that bile gland for now, at least until you get back to civilization (and an alchemist lab). Cast Gentle Repose ASAP (it'll even cover all the parts you've already cut out). Then go find a buyer for the corpse, and someone who knows how to treat the gland.
