Why is that important? This is probably that largest contributing factor to their low price.
There simply isn't anything else comparable for the money, unless you start looking at stuff much older. Take the 350Z for example - it was out around the same time, probably the RX8s closest competition, cost around the same money and at the moment is about twice as much as an RX8. The 350z is hardly frugal, either.
You have to drive it pretty hard to achieve 14MPG, mind - I'm talking about a whole tank just hooning. The 21MPG figure isn't too bad - comparable to what my ST did over here tbh.