PASS has a contest going to capture some of the great stories we know are out there - the ones that you took back to the boss and said "this one thing alone paid for the trip". I think it's a good contest and good marketing. Bill Graziano wrote up his story (and rules on the contest), but strangely I couldn't think of a story that quite met the criteria. I've learned a lot and met a lot of people over the years, just never had the one big "aha" that makes a great story. Maybe I need to listen harder! I think that also points out the challenge of justifying any type of conference - you don't know if you'll say Eureka, or if you'll learn a couple dozen smaller things that don't seem all that impressive considered separately, but together add up to an interesting bump in your own knowledge.
If you've got a story I hope you'll enter the contest. If you don't - like me - then we should work harder at keeping track of the things we do learn this year, because even something that seems small to us might be hugely important to someone else, and maybe that helps them get to go next time.