Wheel backspace question

I found this a bit confusing. I recently bought my '04 330Ci. I noticed that one front wheel stuck out from the fender farther than the other. I should note these are the staqggered style 68's. My first thought was somebody screwed up mounting the tire and mixed up a front and rear wheel. I took it to my indy shop and they first checed the front/rear sets were ok. They then pulled the spare (a 7.5") and we measured the backspacing. All three are different. I don't have the measurements in front of me, but they said one is correct, one is 1/4" different. and one is 1" different. Part number ending in 9180 is shown to be correct on Realoem. Other wheels have different BMW part numbers. Not even the dealer can explain this difference. Realoem wants $600 for a wheel. I'll find a used/refurb one.

Anybody else ever seen anything like this?

Wheel backspace question