Sharon,
I'm paying £25 per month and about 1.5% of my sale if I run a credit card, or 20p if I run a debit card.
You can get slightly lower monthly rental and % rates but they come with a requirement to run enough sales to cover their monthly minimum. This is usually £20. So say your % with them is 1.4% but you only run £500 of credit cards that month, you have to pay them another £15 that month.
I felt that this requirement was too much pressure. Although it 'only' translates to around £1500 of sales per month, what happens if a lot of customers happen to use cash that month? Or debit card where the charge is only 20p rather than a credit card?
I didn't want to feel pressured into WANTING my customers to use credit card (just so I could give a chunk of it away to my merchant)!