Is there any payment processor cheaper than Dwolla?
Dwolla is free for transactions $10 and under, $0.25 for everything else.
They are probably going to be losing money on every transaction until they gain enough volume that they benefit from efficiencies of scale.
PayPal "gift" transactions are cheaper (completely free to use in fact), but that isn't for use as a "payment processor".
clearly no on bitcoin, if it takes more than 1 step process then no
Dwolla is more than one step as well (e.g., transfer funds from a linked bank account first)