I looked up that tractor on the JD website. I'm thinking the entire 3pt assembly is optional, so that would dramatically increase the price of the tiller. Because to use the tiller, which may or may not be reasonably priced, you have to add the 3pt.
What would concern me most about that tractor is the ground clearance for use with a tiller. If you are tilling a garden with that machine, I'd suggest you get some tire chains as well becuase that tractor does not look like something that would be good in the dirt.