It depends on the case strategy. If you are filing for your wife, and she lives abroad, you will be paying a USCIS filing fee of $420, and National Visa Center fee of about $318. If your wife lives in the United States, and she is eligible to "adjust" her status, the USCIS filing fee is $1,490.
I would advise consulting with legal counsel to determine the best case strategy to pursue for your wife, and confirm the filing fees for the strategy you select.
I agree with my colleagues.
IMMIGRATION LAW PROFESSOR for 10 years -- LEGAL DISCLAIMER: This answer is offered for informational purposes only. It does not constitute an attorney-client relationship.