There is one ( Nortrac ) on my area craigs list for sale with a rear main seal leak and a rear differential leak. The owner reports it would only cost $600 to fix both leaks. Most tractor shops are above a hundred an hour. At this rate I think he is 25% correct with his estimate. No one is going to tear down a machine in two places, find the problem, buy parts, and assemble for the owners estimate.