Many thanks to the OP for this thread!
Didn't realize that my (new to me) used 2008 335i didn't have an alarm installed in it until I read this and other threads about it.
No beep, beep! WTF?!!
Fortunately, my car is pre-wired for the alarm. So, based on info in the thread, I just ordered an alarm system from Circle BMW in NJ for $243 which is $122 less than the OEM $365 price that my local dealer wanted to charge me. I actually saved another $18 because Circle didn't charge me any sales tax and the cost of shipping was just $13 compared w/about $31 in sales taxes that I'd have to pay my dealer.
My local dealer also quoted a price of $766 for the alarm (including tax on parts) installed, which works out to $370 for labor.
The install instructions at the top of this thread were very clear and easy to follow and after checking the hood switch and ultrasound mounting locations and the pics of the siren mounting requirements, so I decided that I could do it myself, but I'll probably still have to pay the dealer $195 to "program" the alarm to make it work properly after I install it (unless I'm one of the lucky ones whose alarm doesn't require additional programming).
So, my net savings on the labor would only be $175 and total cost will probably be $451 (or about a 41% savings over the dealer installed price), which I think is a reasonable, even though I think the alarm should have come installed in the car in the 1st place.