You have to shop/check OFTEN and jump on it now, I just bought a v2 powerdrive 12v 55lbs from CRAIGSLIST for $200 new in store cheapest I could find was $549 + tax. Otherwise new sad to say for something like I listed walmart is the cheapest.
For $300- $350 you could find a nice used 24 volt cable steer 60″ motor. You just need to check CL every few hours. I found a nice one in the classifieds here a few years ago. DT