It doesn't necessarily have to be that expensive. I have a friend who recently went through a very friendly divorce. Both parties had agreed on who would get what. In Washington State there's a process for these types of amicable divorces where a judge doesn't have to make any of these determinations. They had to pay the ~$500 filing fee, wait 90 days and that was it.

I'm sure it varies quite a bit from state to state though.