The biggest cost component is the motor it seems. Eina... like R20k for a 20kw 110V DC motor.
I've seen some people buying cars with seized engines, pulling the engine off the gearbox and mounting a golf cart motor in its place, one of these people claimed a top speed of 65mph IIRC
As for the 110v DC motor, how much would an inverter for ac cost? Keeping the voltage the same though