BMW issues mid-model-year price hikes fairly regularly. Additionally, they change starndard equipment mid-model-year as well.
MY 2011 was a particularly long model year for the M3 and 3 series, and some other BMW models as well. There were actually three distinct model updates for the coupe in that time, and four for the sedan. These are often referred to unofficially as 2011, 2011.5, and 2011.75 here on the forum. I don't think the final (really just October) 2011 sedans got a distinct name due to extremely minor changes from 2011.75 (I think it was just a minor change in standard equipment). In retrospect, perhaps these would have been better named 2011.00, 2011.33, 2011.66, and 2011.99 but I digress.
Anyway, what you are looking at above is probably a 2011 vs. 2011.75 (or even October 2011 "2011.99") sedan.
I don't recall all the equipment changes over that long model year but there are threads about it on the forum.