When it comes to criticizing BMW's product plan, especially under the heading of cars that are mini versions of each other, it appears that Kate's Dirty Sister nailed a simple truth of value. That is, it costs money.
It's also a matter of corporate one-stop shopping, and getting a helluva bill for the privilege.
BMW drive thru clerk : Good morning Sir, what can we serve you today ?
Client : I'll have one small sedan and one medium SUV.
BMW drive thru clerk : Would like to add 2 extra wheel drive in your sedan for only 2500$ ?
Client : Ahh... well, ah ok, why not.
BMW drive thru clerk : Ok Sir, that will be one 328i Xdrive and one X3, total is 81400$, please advance to the cashier. Thank you and have a nice day.