I'm guessing those prices are for fitting of a hardware box to add carplay. It can be done just by software, it's a hack. The thread on a5oc had details of a guy who could activate it remotely if you plug a laptop into your car. I'm not sure but I think there is now a way of doing it by just plugging an sdcatd in which does it all. Not 100% on this though as I sort of lost interest in it.
There are plenty of places that will do the software for you if you dont want to do either of those two methods though for a lot less than the hardware solution. Theree was something about the hardware so lotions which put me off them, others may be able to advise.
Not sure on the rules of this forum re cracks/hacks etc hence tthe skirting around the topic somewhat.