The other problem with practical pricing on these sort of items is the prospective buyers, at some point in their life, heard of someone who found the item, an HT-20 in this case, for $200 so that's what they have in mind. I've purchased many Bolens/Iseki tractors and yes, I have found some of these "awesome" deals and seen others who have too. The problem is the people who sell these tractors for this price usually don't know anything about them and the tractors seem to have a pattern of having been heavily abused over the years. Wiring is stripped, fluids have either never been changed or have leaked out and continued to be run, tires don't hold air and are bald, multiple leaks, worn out rings, etc. etc. So after you spend the $2k on tires, ring job, leak repairs, and redo the wiring nobody will even reimburse you for the parts because they saw that same tractor for the $200 and it pretty much looks the same as the one that has been gone through or is still working like new. So, I would second the notion that you might as well keep it unless you're willing to give it away because there are few people who understand the value of such items.
My general philosophy on pricing, is I price it for the dollars I have into an item and I don't put a dollar amount on the time I put into them. If nobody wants to pay me for the amount I have into it then I keep it because I'm not running a charitable foundation. My benefit is I get to use the item in the meantime while keeping it properly maintained.