For a guy on 43's that wants to ride challenging trails all day or aren't within 6 hours travel time, I see how Windrock may seem over priced. But I ride a gayzr so less difficult trails can still be fun and there is more fun to be had to the smoother trails. It is pretty easy to do 75 or more miles in one day if you want to actually ride for more than 30 minutes at a time.
Windrock is $20 a day or cheaper the more days you get, up to $100 for a full year. In my mind, if I make it to Windrock for TWO weekends a year (Friday-Sunday), I just broke even. Now if you want to start adding in other costs like camping at 15/day or RV hook up at 40/day maybe, but I don't really know what other parks charge off the top of my head.