The fees that you're looking at are: camping, wheeling at two different parks (up to three days,) food, and gas.
I'd say, depending on the food you eat, the beer you drink, and where you're coming from the trip could easily be done under $500.
That may be a high estimate, but you may have $200-250 (or more) in gas.
Not factoring your gas, you're looking about about $200, IIRC. For more info, hop over to
ECXC (Best Xterra Wheeling Event East of the Mississippi) There is a forum there, once you sign up (does not imply commitment *until you pay*) you will have access and can look for more accurate information.
Hope that helps!
-Jeremy