This is just MY OPINION. I'm not a grad, so take it for what it's worth. Many of the trips that cadets go on, including some of the clubs, is funded in part by the AOG. The AOG supplements many activities that federal funding just won't provide. If you haven't checked out their website, I think you should.
http://www.usafa.org/index.aspx
I personally think it's worth it. We became a member for the 4 years that my son is there. We didn't want to buy a lifetime membership for our son until he got at least into his C2C or C1C year. You never know. Your cadet could choose to leave early. And when my son graduates, I'll probably not remain a member. But as part of our son's graduation present next year, among other things, we will get him a lifetime membership to the AOG. It will be about $650-$700. Somewhere in there. But I know that between certain trips, conferences my son attended, athletics, and all of that first year where webguy and everything else kept us in touch; I think it's worth it. When I think of how much money I saved on college for my son, it doesn't bother me to contribute.
But again; this is just my opinion. There may be some that haven't used any services from the AOG. And maybe their cadet doesn't feel anything towards it. Especially if they are already set in their mind to do 5-and-dive. But for me, it's worth supporting.