Banks and other credit card issuers are nervously awaiting the new credit card law set to go into effect on Monday. Many are anxious to determine just how big of a profit hit they stand to suffer as a result of the CARD Act.

Judging by early estimates, it could be quite costly.

Late last year, JPMorgan Chase (JPM, Fortune 500), the nation’s largest credit card issuer, warned it expected its credit card business to lose as much as $750 million this year as a result of the new legislation.

Executives at rival Citigroup (C, Fortune 500), which issues cards to consumers from Maine to Mexico, warned last month the revenue lost by its domestic business could tumble anywhere between $400 million and $600 million.

All told, the new law is expected to cost the industry as much as $5.5 billion in lost revenue this year and more than $50 billion through 2015, according to the credit card advisory firm R.K. Hammer.

Much of that decline, experts said, is due to the fact that issuers are severely restricted by how and when they can raise a cardholder’s annual percentage rate.

Under the new law, lenders are not only prevented from raising rates on a customer’s existing balance, they are also required to wait 60 days before raising rates on delinquent customers.

Hoping to compensate for some of the lost revenue, credit card companies have introduced a dizzying number of new fees and raised existing ones since the bill was signed into law last May.

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