The ones I have seen listed for sale were not terribly expensive, I'm thinking somewhere in the $3-5,000 range. They are just so darn big most folks don't have a truck big enough to move it, a shed big enough to store it, and most of them take a couple guys to crank. Not exactly the thing you can just roll out of the corner of your garage and fire up while you sit in a lawn chair and let it run. 30 years ago someone was liquidating an oil lease in West Va. and was selling a bunch of them---take your pick $600--you had to remove it from the pumphouse. We thought about going to get one, and then common sense prevailed.
It looks like that one is running on gasoline. Looks like a fuel tank off a baler or combine rigged up above the cylinder.