What is the fee for Form I-829?

$3,750 effective November 23, 2010.

The filing fee changes often. You can find the updated fee on the USCIS website.

$3,750, plus $85 for biometrics.

This is strictly from the USCIS website. The filing fee is $3,750. A biometric services fee of $85 is also required for the petitioners, as well as any current spouse, former conditional permanent resident spouse, or conditional permanent resident children that are included on the petition between 14 and 79 years of age. That means you must submit a separate biometric services fee of $85 for each conditional permanent resident who is applying with you to remove the conditions on their permanent resident status.
You may pay the fee with a money order, personal check, or cashier’s check. When filing at a USCIS Lockbox facility, you may also pay by credit card using Form G-1450, Authorization for Credit Card Transactions. If you pay by check, you must make your check payable to the U.S. Department of Homeland Security. Service centers are not able to process credit card payments.