Another thing to stress here is that a sports/luxury car should be just that; a luxury.

Cars, generally, are a rapidly depreciating asset -- particularly expensive ones. To that end, you shouldn't be spending money you don't yet have on them, i.e. financing. Wait until you have enough money to straight up buy it, or don't. It's not worth losing out to depreciation AND interest charges.

The only real exception to this is:
(a) You already have the equivalent capital, in hand, invested.
(b) You can borrow its equivalent at a particularly low interest rate (e.g. 2%).
This depends on (a) sustaining a higher rate of return than (b).

It really depends what you're looking for. Luxury and Sport cars can have very different operating costs; a Lexus does not really have comparable maintenance requirements to a BMW/Porsche/Mercedes. Personally, if you're looking for a sports car, I'd recommend the first two (vs Mercedes). I daily drive a 911TT & Boxster and the running costs are fairly reasonable. The two things I'd call out here are that tires are much more expensive (and require more frequent replacement), and that regular maintenance tends to be on shorter mileage intervals. In general, expect all consumables -- I mentioned tires above, but things like oil are also worth calling out here -- to be at a premium. In terms of ballpark costs, a service where not much happens (e.g. filters, oil, etc) will probably cost you a few hundred -- and a more expensive service (e.g. cv joints, brakes, etc), a few thousand.

stoichiometry: it does not mean what you think it means.

http://www.rakis.net/~newby/car2.jpg

http://www.rakis.net/~newby/car1.jpg

2011 Turbo S - 6k miles
2003 Boxster S - 77k miles

https://lh3.googleusercontent.com/-65WLowvDztQ/UzkLzfRBxzI/AAAAAAAApPo/ZomEM3gC-EI/w954-h716-no/IMG_20140330_194042.jpg

The Prius in its natural habitat.