I have bought one of these 750W Motors just 2 weeks ago from www.kornetshop.com.
It called there JM-822/750 and cost 172€ +5€ shipping. The same part in Ebay is 195€. Except different connectors and namedplates it seemed, all of this Motors comes from one or 2 chinese factorys. If one would buy it from china, they are much cheaper, but it can last weeks to months, til you get the Motor.
I need it for another machine, so I have tested it, it runs with a potentiometer/rheostat (don't know which word is better) and runs from 103rpm (not really it sounds bad) from 300rpm it sounds how it should be. It works up to 3900rpm, maybe constabs Motor runs at fast, if the maxspeed is changed within the parametre list.