Square charges a credit card processing fee of 2.6% + $0.10 for card reader transactions, 2.9% + $0.30 for emailed invoices and 3.5%+ $0.15 for manually keyed transactions. QB is 2.4%, 2.9%, and 3.4% +$0.25 respectively. So the cost is pretty much the same.
Bottom line is those providing the card processing service are the ones making easy money.
To the consumer making a $25 purchase, they sort of don't even notice and like the convenience of using the card.
To those accepting the payment, they lost maybe 2-4% of what they could have made, adds up at the end of the day, but at same time they might have sold more than they would have if not accepting said payment methods. This kind of critical for the restaurant business, small shops, convenience stores, even many big box stores. Any place that makes lots of individual sales transactions every day.
Might not be so critical for service businesses that make limited number of sales transactions a day. Those tend to be higher dollar amounts in the transactions they do make, so where the other businesses I mentioned before maybe still have a big mix of cash payments mixed in there, this group could end up having that 2-4% taken off the entire day's sales in fees on the payment method if all the sales of the day are paid by credit card.
If you are a retailer and are liquidating certain items, say already taking a loss- if customer uses credit card you kind of taking even more loss on the item.
You can bet most retailers already have a certain amount factored into their base markup of many items to offset this cost they pay for accepting credit card payments. Consumer does not see it itemized in any way but it is effecting the marked price.