A bargain indeed! I paid £50 for my G7e off ebay - it needed the cable repairing.
Are you sure its the drivebelt? Many a time the tech drive stops working due to the slider mechanism over the motor seizing up, so that it doesn't operate the actuator lever when the handle is moved back and forth. I got a G4 with that issue - they had stored it in the garage for years and then came too use it and the tech drive slider mech had seized. disassembly and oiling soon sorted it.
But its a crazy thing aint it that we can pick up a Kirby that would have originally cost over a grand for just a few quid!
Come 2017 when the new EU rules kick in and the motor wattages are reduced, these will be back in demand again as they pack a great deal of suction power for their low wattage.