You have to avoid the calipers rebuilt by the vendor for the lowest cost. Note that this is not always the lowest selling price part. When the seller squeezes the vendors too hard, you get cores that should not have been rebuilt, using parts that should not have be reused.
when they retail a complex reman part, like a loaded caliper for 40, reman starter or alternator for 50, that is very little money for cleaning, new parts, good assembly and testing. Mark up by some retailers is much higher than others, and some squeeze more than others. Brand A squeeze's vendors too hard this month, brand B does it next moth. Makes it a crap shoot. Retailer reputation is about your only tool. I use Napa, and so far so good. They do cost a little more. When they burn me, and all vendors get greedy, I will change.
Rod