I found a used Caroni 4'er last spring for $600. and it was worth every penny! Knowing now how great the tractor tillers work now, I would pay the money for a new one if I had to.
This tiller chews up the soil so well that it looks almost like saw dust. It makes my walk behind look like a toy. The pic is from last spring, you can see how fine the soil is and I don't run it at full PTO speed.
I'm also tilling a small plot for a friend up the road, you might try to swap out tilling for friends and neighbors to justify one.