It costs too much because the only sell it as a package: (1) heater and (2) air hoses.
And you CAN buy it aftermarket. Any decent garage shop has a supplier that have these things. I am telling, I saw the guy making the phone call in front of me, and they delivered the hose 20 minutes later. It is not the same exactly shape, but it works. My car been running since that (i know, running a little HOT, but running

)