This is weird. My brother will probably chime in on this, but from what he told me, one side of the rear pads was worn pretty bad and the other was pretty much shot (uneven wear on the sides). He took it to one place and they said he needed $500 worth of calipers/pads. He said forget it, took it to another place where the guy was real nice. He said the pads were worn and the rotors were grooved. He turned the rotors and put new pads on. I'm sure my brother asked to see everything. He hasn't texted me complaining that it's still making noise.
I told him to bring it over to my house and we'd mess with it this weekend but the car is his DD, he's in college now and works every single weekend. He just paid to have them fixed.
Could maybe the replacement calipers have been faulty and sticking, causing premature brake wear? The rear calipers on these cars suck anyway, and I woudln't put it past faulty rebuilds. The first place said the calipers were bad, the 2nd place said they were fine. This is why I now work on my own shit, but he had time constraints and doesn't have the luxury of owning 4 cars to swap out and drive something else until his is fixed.