Many bank customers have long felt nickeled-and-dimed by fees imposed by financial institutions. But now some banks are demanding much bigger denominations.

The region’s largest banks are charging consumers as much as $50 a month if they do not maintain minimum balances or meet other requirements for certain high-end checking and savings accounts.

Citizens Bank charges customers $50 a month when the balance in a top-end money market account slips below $1,000. Sovereign Bank imposes fees of up to $30 a month, and Bank of America and TD Bank each charge $25 a month whenever customers fall short of minimum balance and other qualifications for some premium checking accounts.

“I haven’t seen anything like $50 a month before,’’ said Greg McBride, an analyst with Bankrate.com, a website that tracks bank fees and interest rates. “That’s a steep price to pay.’’

The sticker shock is the latest sign that US banks are pushing fees to new heights to boost revenue and shed unprofitable customers with slim balances. Since 2009, banks across the country have more than doubled the average monthly maintenance charge for basic checking that does not pay interest, to $4.37, according to Bankrate.com.

But many of the nation’s largest banks now charge $25 or more per month for premium accounts that offer higher interest rates, free checks, or extra services.

The average fee for interest-bearing checking tops $14 a month nationally, up from $12.55 in 2009. Some institutions may waive the charges if customers complain, as is the case with most bank fees. Bank profits have been pummeled since 2008 because of steep losses on mortgages, tepid demand for loans, low yields on investments, and new regulations. The biggest banks have lost billions of dollars in revenue from new rules reducing the amount they can collect in debit card fees and limiting overdraft charges.

“Banks have been trying to recoup some of those lost revenues or get rid of accounts that are not cost-effective,’’ said Richard Barrington, senior financial analyst for MoneyRates.com, a financial website that tracks bank rates.

Spiros Aloupis, a Citizens Bank customer in Revere, said he was shocked when he received mail advertising the bank’s Performance Money Market Account and saw the $50 monthly fee for letting the balance fall below $1,000 on any day during the month. Aloupis said he thought it was a mistake, until he called and Citizens confirmed the fee.

“Isn’t that ridiculous?’’ said the 86-year-old retiree, who has a safe deposit box with the bank.