2000 Toyota Celica Excessive Rear brake wear

I have a 2000 Toyota Celica GT-S that has been burning through rear brake pads like crazy for the last few years. Typically every three months they start to grind when stopping and require being replaced shortly after. It is my understanding that rear brake pads should not need to be replaced that often in a front wheel drive because the front brakes do the majority of the stopping. What could be causing this excessive wear and how much should I be prepared to spend to have it fixed?