The government charge at the port of entry or the employer's petition charge, plus the state licensing costs, verification charges and any credential evaluation.
Licensing is usually the larger and slower expense
On the immigration side a Canadian citizen pays the charge applicable to an application made at a port of entry, or the employer files Form I-129 and pays the petition charge, with premium processing available at additional cost; all of these amounts are published in the USCIS fee schedule and should be confirmed at the time. On the professional side the state board charges for the licence application, for verification of the Canadian registration, and often for fingerprinting or a jurisprudence examination, and the Canadian regulator charges to send verification directly.
Add courier costs and, where the degree is from outside North America, a credential evaluation. Ask the employer in writing which of these it will reimburse and when, because staffing companies vary widely and a verbal assurance during recruitment is not a term of employment.