I'm surprised by the amount of responses on this thread in regards to using iPhones in cars with AUX. BT transceivers with A2DP can come @$20-30, with some giving pretty good sound quality. I just plug my phone in, hang it on my magnetic dock, and BT connect, which is nice as anyone in my car can connect to that transceiver and play their music if they want (kids, wife, friends)
Edit: the convenience of not having to go through AUX cables alone is well worth it. I think I burnt through 3 AUX cables before I bought my BT. Now I have hands free and don't need to plug anything in my "dumb" car