I live in southern Grayson County, Texas. There really aren't many small tracts available. Building sites of 3 acres or so are $50,000 - $60,000. One acre lots are $22,000 to $50,000 depending on terrain, trees, creeks, etc. There are rare 10-acre tracts for $7,000 or $8,000 an acre and up.
Further west a few miles, there are 5-acre tracts with water for as little as $5,000 an acre - flat and no trees. I have 24 acres in this western area, but have trees and a creek. Gave a little over $3000 an acre in 1998, but is probably $5000 an acre or more now.
There were 100 acre tracts sold maybe 5 years ago for as little as $1800 an acre, but they are now double that, at least, for large tracts.
Small half-acre lots are at least $17,000 in all the developments I know about.
This area is 50 miles from the middle of Dallas, but growth has almost reached us.