In order of importance for the developer: (IMHO)
1) Networking aka drinking with nerds aka making new friends
2) Learn about your peers (see #1), what they're doing, their passions, and their visions for the future
3) Learn new technologies. Different types of learners means that some people are more geared towards instruction based knowledge transfer.
4) SWAG
For the company:
1) Recruiting/finding the best and the brightest. Conferences are a good place to recruit and sell your company on an ad hoc basis. Not advocating poaching by any stretch, it's just good to know who's out there if they are looking for a change.
2) Learning that can then be passed on to coworkers. Your company won't send everyone, so they'll want to send someone who can bring back knowledge and transfer that locally.
3) Keeping you happy. $2000 may be a lot, but if they know you're a good employee and you'll stick around for awhile, that's an investment, especially if you can do #1 and #2 while you're there.
Keep in mind that the reasons you want to go are not necessarily the same reasons your company may pay for you to go. They could say no, in which case you can ask for a reasonable explanation why, and then you can better formulate a response when the next conference comes up.