The $70 is an investment in your future career. It is your chance to show the higher ups (and your troops) that you're "one of the boys", that you'll play the game, and that you belong. It's an enforced social occasion where you see and be seen, where you bond with the people your life may depend upon one day. If they only know you as a set of stripes, then they may not be too motivated to save your butt when it really counts.
See how many people who rank above you are there. You ever want to get to that level, you play that game. Plus, who knows...if you give it a chance, you might actually like it. If you don't, then put on an appearance, drink in moderation, and leave as soon as custom and manners will permit you to do so.
Just remember, you don't have to be everyone's friend, but you can be a good comrade to all.