Compare what it would cost to hire someone to do the tractor work. That should be the discount. But they would end up owing you a free membership plus more money. A tractor is a farmer's livelihood. Are the lawyers and accountants in the club handing out 20+ hours a year of legal and tax work to members in exchange for a $300 discount on club dues?

Hunting club land is some of the hardest work on tractors and equipment in terms of wear and tear and stuff breaking. It's usually once a year mowed/plowed thick overgrown brush and not the well maintained row crop fields tractors are designed to handle for daily use. And like you say, everyone has a good idea for where a new plot should be and asking you to push the tractor to its limit to do what you really need a dozer, mulcher, etc to accomplish.

If tractor guy enjoys it and sees it as volunteer work to help his fellow club members have some fun, then that's about the only good reason to do it. If the club treats it as transactional and no one seems to care how much you are helping them out, then tractor guy is always getting the short end of the deal.