The state licence application, the credentialing organisation's certificate, examination and verification charges, and document delivery. These usually exceed the immigration charge itself.
The professional charges are larger than the immigration charge
The immigration side is comparatively modest: a Canadian citizen pays the charge applicable at the port of entry, or the employer pays the petition charge if it chooses to file Form I-129, with amounts published in the USCIS fee schedule. The professional side is where the money goes. A state board application carries its own fee, as do verification of the Canadian registration, fingerprinting and criminal record checks, and any jurisprudence examination.
The credentialing organisation charges separately for the health care worker certificate and for the credential review that supports it, and transcripts and licence verifications sent directly by institutions each carry a charge. Budget for courier costs and for the possibility that a document must be reissued. Ask the hospital whether it reimburses any of this, since some employers do, but do not assume it.