Surface prices

My siblings and I have received an offer to purchase approximately 55 surface acres of that we have in Sec. 14, Blk. 72 PSL. This area is right outside of Toyah, north of I-20. They want to put in a "well park," and have offered $500 per acre. I know nothing about the value of surface only in this acres and would appreciate an idea of what this should be worth, or what to counter with. Any help will be appreciated.

Tommy Beauchamp