For example, "free" is a magical number.
Anything under a penny per transaction is as good as free, when the nearest competitor is PayPal.No, that's the point: 0 is a magic number in our heads.
"1/50'th the cost of Paypal" will get, say, 5% of the people to switch.
"Free" will get 50% to switch.
(numbers pulled out of my ass, of course, but you get the idea)