The cost is going to probably be mostly for their labor, and not so much the part. This is because the part takes 2 minuets to replace but the entire brake system MUST be bled. :mrgreen:
It'll be bleeding all four brakes in order (usually FD, FP, RD, RP). If you have ABS I do believe there is something different you do during bleeding (I think it is when you compress the calipers), but I don't have ABS so don't know specifically what. :mrgreen: