If you don't mind the 'add-on' style, you can get one and install it yourself for less than 1/4 the price. You have to put up with a few extra cables (antenna and power) but at least I can remove it easily and use it in another vehicle or sell it.
It's not for those that like a 'clean' look....my wife doesn't like it. But my Sirius radio does some things that her oem/in-dash unit can't do, so it's a trade-off.