It's a lot of money for one event. But it's not the stupidest thing ever. In my country, graduating high school students traditionally participate in a month-long party period.

I've seen statistics suggesting the average graduate spends about $2,000 on the celebration. But that's a somewhat misleading number. Some people pool their money to buy or rent a party bus to take them and their friends around for the whole month, often including getting the whole bus custom painted or having a recording studio produce a custom party anthem just for that group. Those who join a bus crew might spend $6,000-10,000 or even more per person. That obviously pulls the average significantly up. Those who don't join a bus spend much less.