All been said really, my rear caliper seal failed in exactly the same way.
OEM calipers are expensive £200 for the rears, I think it's around £180 for fronts (each), I had a refurbed OEM one from my local car parts place for around £50 iirc.
They are OEM one's that have gone back to a factory for refurb, it's a lot cheaper and it is a genuine OEM caliper, you also get money back on an exchange basis.