Some interesting ideas here. What I'd suggest you do is figure out the profile of your desired buyer. Do they have children? Do they have a long commute to work? Are they retired? Are they in the military? [Note to you and to the Realtors reading this: Don't panic. I'm not suggesting steering or anything of the sort. But it's reasonable to guess who is most likely to buy the property.]
Then figure out what incentive might work best to attract your most likely buyer. Someone with a long commute might like "Free Gas For A Year!" And it won't be horribly expensive...at least not until gas tops $5 a gallon or so. Consider: If someone commutes 20,000 miles a year, and they drive a vehicle getting 10 mpg (pretty wasteful, there), then they'll use 2,000 gallons of gas a year. At $3.50 a gallon, your cost would be $7,000...far less than you're considering paying out. A more reasonable calculation of 15,000 miles a year at 15 mpg results in 1,000 gallons of gas used.
So, figure out who your target demographic is, and then put together some package that might cost, say, $5,000 a year, more or less. Someone who needs a car? You pay a year's worth of lease payments. ($300 a month for 12 months equals $3,600. You might even go 2 years, perhaps with a slightly less expensive lease.) An "alpha male" who wants to be the next Ultimate Fighter? That's easy. Karate/kickboxing/Brazilian jiu-jitsu lessons cost roughly $1,500 a year--at least in Northern Virginia for 2 -3 times a week lessons. If the family had teenagers (teenage boys, especially), you could offer weekly pizza parties. I've heard of this being done for rentals near colleges. A couple of pizzas from Domino's or Pizza Hut cost about $20. A year's worth, once a week, would cost about $1,000.
Anyhow, you get the idea. You can add a lot of sizzle to the package. Just get/stay creative.