It's possible for calipers to freeze up. but $260 each? that's nuts... you can get rebuilt calipers at nopionline.com for about $70 each, new brembo blank rotors are about $17 each, and pads are $20 for both sides (less than $200 total for all parts). installing calipers is fairly easy, the problem would be getting the frozen caliper off.

You can also try the junkyard for parts, ALL 3rd gen (88-91) REAR brakes are the same (the front ones are different between the Carburated models and Fuel Injected models)