Well i had mine done (new 32 gtr calipers) and a seal kit is only $42
Like gts4diehard said, to rebuild them cost $110 (includes gst, and the cost of the kit) So for me the $58 i paid for them to do it was well worth it in the end, as the fully strippeed them, cleaned them, and painted them
Well worth doing, and you will find that the pistons are ok, unless your dust covers are falling apart, they will be fine.