"Almost no one understands how PayPal actually worked or why it took off when other payment systems before and after it didn’t. Most of the people at PayPal don’t understand this. The reason it worked was because the cost of transactions in PayPal was lower than any other system. And the reason the cost of transactions was lower is because we were able to do an increasing percentage of our transactions as ACH, or automated clearinghouse, electronic transactions, and most importantly, internal transactions. Internal transactions were essentially fraud-free and cost us nothing. An ACH transaction costs, I don’t know, like twenty cents or something. But it was slow, so that was the bad thing. It’s dependent on the bank’s batch processing time. And then the credit card transaction was fast, but expensive in terms of the credit card processing fees and very prone to fraud. That’s the problem Square is having now.
...
So because about half of PayPal’s transactions in the summer of 2001 were internal or ACH transactions, then our fundamental costs of transactions were half because we’d have half credit cards, we’d have that and then the other half would be free."
from book
