Credit cardholders can pay just over twice the 3% base rate - Barclaycard has one piece of plastic that charges 6.8% - or a massive 13 times at Vanquis with its 39.9%. And that's just published rates as some cards hit holders with poor credit records with even higher annual percentage rate (APR) interest levels, some top the 60% mark.
So can holders expect a fall now the base rate has hit a 50-year low? The banks claim they can't afford it, card rate cuts are not on the agenda. Barclaycard, the UK's biggest plastic lender with 12m accounts, says the cost of financing cardholder spending is a small part of overall expenses so changes in base rates are insignificant.
Most costs are not interest-rate related. Sending out plastic cards, replacing those that have been lost or stolen and posting monthly statements are among the expenses incurred before borrowing to finance customer spending.
But one of the biggest costs comes from cardholders who default. Banks are guarded over figures but the higher cost cards such as Vanquis and Capital One Classic go to those with poor credit ratings - they've missed payments or had county court judgments or have moved home several times. At the other end of the scale, triple A-rated holders can pay under 10%.
About half of all customers pay their bills in full each month, incurring no costs, subsidised by interest paying holders.
Many credit card rates have remained unaltered for two years despite eight base rate moves - both up and down - since January 2007.
A number of cards are still on the same rates as 2005.
But the APR rate is only part of the story. Banks make money in penalty fees, extra costs for using the plastic overseas and from the percentage - typically 3% - levied on balances moved from one card to another.
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