Frog,
Actually, the USFS cabins start a $25, and top out around $45 a night. Some have wood stoves, but many have oil stoves, and you have to bring your own fuel. So that adds to the cost.
Plus, most are only accessible by boat or plane, so that adds cost too.
Still, at least down here in the pan-handle, the cabins are well used and apprectiated.
There are State owned cabins up north, and I don't know the deal with them.