Prestige price tag. But these days, especially, there is a lot less difference between something like a CX-9 and a 'luxury' crossover, as is the case with the sedans and sport coupes. Have you noticed the recent trend of luxury manufacturers adding even more gimmicky features to try to justify the extra $$$$? (Self parking, seat belts that hand themselves to you, air flowing THROUGH the leather seats, etc. That's why resale values on those cars is zip. They depreciate a lot more when you drive them off the lot than a regular car.
The fact is, I'd take the CX-9 over any of the more pricey cars anyway, even if the cost was the same. Mazda put a LOT more thought into how things work practically, and less into "gee whiz" gimmicks that I'm too able-bodied to need anyway. It's more stylish, has more room, and will perform at least as well as them, other than possibly the Cayenne Turbo. Cheaper to own, too. Game over