I'd have to agree with the folks posting to purchase a dozer/excavator or hire one. The price you posted seems very high for lot clearing, especially for a lot with no structures to worry about. Remember, doing it yourself is going to be a big undertaking in removing the trees, never mind getting rid of them and stumping the land, then grading it. Do you have a use for the wood? A tractor is fine for the occasional smaller stump and grading, hauling logs etc. I just wouldn't want to do it myself clearing 3 acres, even with a 100hp tractor, not to rain on your parade.