The Texas State Park system offers a park pass for $75/yr.
This covers your entry fee's, 5 or 6 half price credits for the second night and 10% off at the camp stores. It will pay for itself in 3 trips with a family of 4.
We used to use ours mostly for fishing up and down the gulf coast. Now we use it mostly in lieu of hotels. I'll have it at Livingston KOA this weekend to go to a funeral and Lake Waco next weekend for a wedding. I don't care if I pay more or less than a hotel, I get to sleep in my own bed that didn't have dogs or who knows what in it the night before.
You ONLY get $$ out of it if you use it. Otherwise it's $$ sitting in storage.