Holy Mackarel....

2500 for control arms? That is some kind of record price. Seriously.

They are almost surely using no-name aftermarket parts, calling them 'OEM". (See my sig for the real meaning of OE and OEM).

Going with BMW parts, it is $600 in parts and MAX 4 hours. (A good mechanic can do it in under one hour). Add the alignment.

IMO you need to leave this shop and never go back. Unfortunately, they have decided you are a mark to be screwed over. Even if you cut the prices IN HALF, it is still a screwing.

THis work is not hard nor is it particularly delicate nor does it need great skill. An easy DIY.

Find someone who isn't going to take a summer vacation in your job.