Charging You to Invoice

This is a new one to me – McGraw Hill is now charging independent contractor to submit invoices. They are deducting 2.2% for an administrative fee when submitting invoices via their platform, which is the only way to bill them.

Out of curiosity, what would happen if the contractors added a 10% administrative fee to their invoices? I understand that accountants like to have a line item for every budgeted expense or revenue, but this is just getting silly.