https://www.wilemotorsport.com/ is the only shop I know of down your way that has a good reputation.
The shops are not trying to rip you off per se. They make a mark up on the parts. So even if you paid the same for the parts they might get to make another 15-20% on them. By doing the job for you they are immediately making less money than another customer. If you are a busy shop, why do it?
Also, customers routinely buy the wrong parts. You get in there to say change the rotors. You take all 4 off only to find out they bought the rotors for the e92 not the e90. Now you have to put everything back together and charge them for the labor. Or it sits and occupies a lift while you wait for the right parts to show up that you the shop sources because you can't trust the customer not to fuck it up a second time.
Basically, if you are buying your own parts, expect to install them yourself. There is a reason most shops do not want to take on jobs with customer supplied parts, which you are now finding out. IF you want to supply your own parts, find a shop 1st that is willing to take on the job.
Just my experience over the years.