Rotors and pads aren't that bad to go non-OEM. Most of them end up sourcing them anyway, so if you find out the supplier you can get the parts for a fraction of the price. You can get some good Brembo's for about $67/piece. Depending on type the price starts creeping up if you get them drilled, slotted, special coated, cryo treated etc. But I typically ball park a high quality brake replacement to be about $100/corner for a DIY and about $200-$250/corner for a OEM dealer installed.
I've tracked a number of rotors/pad combinations and found the majority of failures are either installation related (failure to bed, clean, are common) or driver related (overuse of brakes) While they exist, rarely are failures hardware related (ie, seperation of the rotor) in my experience.
But eithe way, $1600 for just rear brakes seems really high. A brake job is roughly 2 hours book time (and that's for all four!) The labor rate would have to be assumed to be at or over $300/hour to get the math to work - which would be absurd.