How much on average would it cost to repair cylinders in the rear brakes of a toyota corona?

someone is offering me a toyota corona but it nedds the cylinders in the rear brakes fixed. I was wondering if anyone would have an estimate of how much this would cost?How much on average would it cost to repair cylinders in the rear brakes of a toyota corona?Wheel cylinders for that car would be less that 30 bucks apiece and about 100 bucks labor to install