Most contractors charge by the hour, $50 to $65 an hour depending on tractor size, with a 14 ft. Batwing 12 acres could be cut in 2 to 3 hours. It may be a move in time because of small acreage.
Their are some contractors that use a small H.P. tractor with a 5ft cutter and they charge $50 an hour , they can only cut 1/2 to 1 acre an hour. You will need to shop around for best prices.