For me it's simple. If I'm doing the work, I buy the parts at the best price I can (generally right here at PartsShop). If I have my Tech do a job, it's with his parts at his price. I've even brought him a 6er of Becks as a thanks (to repay all the info gleaned from his Stuttgart training plus odds and ends from the parts car).
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.