Best sports cars do have muscle engines which can outrun even the fastest sedans easily. A sports car engineer therefore puts it first on the list of factors that he has to consider: how to travel the distance with the least amount of time possible.
A number of sports cars compensate for a not-so-powerful engine with a light body, paying due respect to the laws of physics: the lighter the mass, the smaller amount of force required to move this mass. This is also the reason why a sports cars usually are smaller, and do not have backseats. If these cars do have backseats, these are not as convenient as a sedan's and is only a throwaway to please the insurance companies. One may also notice that a sports car quite often only has two doors, and it shares the same reason as that of the backseat.
Buying a sports car does not have to mean going to your nearest car dealer and getting a brand new vehicle off the rack. There are quite a handful of these vehicles beyond the dealer's garage, in very good condition and sold at a lower price. You can always check out car auctions and watch out of sports car models being sold at pancake rates. Pre owned sports cars are always available on your local car magazine or website, sometimes it just requires you to pay more attention to these ad placements; you'll never know when the sports car of your dreams is right under your nose.