There does seem to be an error, try annual $250 with 500 transactions, yields all zeros.
Also it does not seem to be taking into account Paypal's volume discounts:
Also it does not seem to be taking into account Paypal's volume discounts:
Doesn't seem to be taking into account the volume discounts.
As a potential customer, the more significant barrier is customers not knowing what Dwolla is therefore not making a purchase.