Tractor mounted Zamboni's have been around a long time. The first job I had in 1980, the town had one on a Ford 2600. They used it in the indoor rink with studs in the tractor tires. They used the tractor for mowing and other chores in the summer. Once they bought a self propelled Zamboni, they used the tractor mounted one on the outdoor rink. I would bet the tractor mounted are a whole lot cheaper. There was show on Discovery a few years back all about the Zamboni. The blades to shave the ice are razor sharp!