That sounds really high. When I got my heat pump I also got a backup air handler with it. Basically that is an electric furnace that sits in my basement and when the temp drops below freezing it heats my house. Some company's try and get rich off every installation mostly the ones that are geared more towards homeowners. I got 3 estimates when I got mine one was close to 11,000 (geared towards homeowners) the other 2 I called guys I knew from different jobs they both came in around 4700 I used the most local guy for service reasons and it works great. I could have a geothermal installed for under 11,000 you might want to call some different people to get your estimates.The problems with heat pumps are the up front cost is high, and in my neck of the woods they don't produce enough heat in the winter by themselves, they need some sort of supplemental heat. What you use is up to you. Some use an electric coil, some use a gas or oil burner.
I want to put one in my place, but I can't swallow the $15,000 I was quoted.