you guys are only looking at 1 side of the story....
brakes.... WTF do you think a set of drum brakes is going to think to a 300hp car?
Gearbox. Lets say a recon box is R5000. Thats R5000 every time you decide to dice that Porsche Boxter next to you at the traffic light. Not to mention towing costs....
Decent tires to handle the power and the higher cornering speeds...
Great conversion price.... R15000 straight into the grave.
Seriously though.... all the works required to do it safely and reliably and you prob talking closer to 30 or 40K total, if not more.