$375 to replace rear pads & rotors. Labor rate at $88 is good. Pads at $91.95, roughly a 25% markup there. Rotors at $160 (for two), an even larger markup (unless sports quality rotors were used - which doesn't make a lot of sense considering it's a Buick sedan).
No issues with quality of work, but Howie's Auto offers the same (or better) quality and doesn't mark-up the parts as much as these guys.
Only way I'd come back here is if I order my own parts from Amazon and bring them with me (which means they won't warranty the parts, but that's standard).
Unfortunately Ernie wasn't in the shop today, so I had to deal with David. Based on my experience today vs what I've read here, avoid David and deal with Ernie.