These are the OEM Potenza RE050a RFT's that came on my 2011 335xi. The sizes are 225/40R18 and 255/35R18.
New re050a tires come with 10/32" of tread and are new on tirerack for $290 for the fronts and $360 for the rears.
Since about 93% of the usable tread on the fronts remains, a fair price is $270/per front tire, and $335 per rear tire.
These guys are nearly brand new! I'm prorating tirerack pricing according to how much tread remains down to a barely usable 3/32".
When viewing these, keep in mind that new tires come with 10/32" of tread. The tread depth gauge cannot even show any wear on the rears!