Anywhere from $5-10k (you have a mate with a truck and a grader, just buy the gravel at a good price) to however much you want to make it.
Seems to me anyone who can make a gravel driveway for a rural property should be able to make you a bit of a runway.
Mine is nothing more than the already hard sandy soil smoothed out a bit. Steel mesh (like they put in concrete floors) weighed down and dragged behind a 4x4 works well. We'll see how it goes when the rains come - first year here...