What a bunch of jerks.
There are two possibilities here.
1) The BMW salesman is a jerk (standard form).
2) You had been driving well over 15-20 when you struck it.
If the impact against the wheel was significant enough to merit a steering rack replacement, it would have been enough to knock the damage or move the subframe (although they haven't classified a new frame as one of the items that has to be replaced). Bring it down to the ordinary Joe's garage, tell them it's not driving properly, and have them look at it on the ramp.
You've made the one mistake you shouldn't make with a BMW dealer: you've been honest and could have seen you coming a mile away.
At that speed, I'm going to guess you've slightly (and I mean slightly) bent the drivers side track rod.
Less is more.