Perhaps there are set certain criteria for a car to be classed as a 'super car', but if there are I don't know :?
Take a high end Marque such as Porsche or instance, I wouldn't consider a Boxter to be a super car, but a GT3 or and RS maybe, now they are pretty special.
Do you class it on speed?? price?? an Mitsi EVO MR FQ340 is not a super car, but with a 0-60 time of 4.4 secs and a very illegal top end its gonna keep up with some pretty special machinery, but 'only' costs £33K
So the nicer Porsches are up around the £100K mark and I would consider those super cars, I think, but for the same money you could be calmly cruising in a Merc SL55, not really a super car though