Ok, now break it down and see where all the expense's are. Unit itself, exchange pipeing, ducting, how big a unit, excavation, material and labor. My guy broke it down so I could see all the figures and do some work ourselves. It helped, but was still more then conventional system. Now subtract the price of a complete regular system (heating and cooling) and the 30% refund on the tax credit - it's not as scarey as it first looks. I'm guessing, it's about 3-4 grand more - that will pay back in 5 yrs or less and last much longer.
Remember, this is your heating and cooling system, it also should help heat your hot water for demestic use for additional saveings . . . . . It's always the initial shock that makes a guy thing it don't pay, a guy has too look long term and the return on investment . . . .

My cheap/frugel son in law couldn't stomace the price either, untill we broke it down and compared to conventional system . . . . Now he's happier then heck that he went with it.

It depends on your equipment also - it cost more to have the units that are large enough to handle the complete home in the coldest winters and warmest summers. Some of the comments relating to that's too high, well, as compared to what? What equipment did they have? I would get 3 or 4 bids and make sure they are all bidding the same sized unit. Good luck