It shouldnt cost you $400. I got mine done for $150.00. Make sure to present your immunization/vaccination records (if you have them) when you go to get your exam done. Otherwise, it might cost you another $100 or so. If you are tested positive for TB (which is one of the tests they do), they would require you to get an X-ray to prove that you dont have active TB which might take an extra day or so.
I got my report in 2 days (add a day or 2 if your TB test comes positive). Its a good idea to get it done way ahead of time though.
GOod luck