I don't know the US market, but I do know the EU market. Here you can simply open ordinary business accounts with different banks. ( Costs not even a 100 a year

I don't know the US market, but I do know the EU market. Here you can simply open ordinary business accounts with different banks. ( Costs not even a 100 a year ) All charge different prices for single transactions or batches of transactions. And more importantly, all allow for transactions to be send by their preferred format. Generally, their price goes down as your volume goes up. Let your system do the math ( Pick the right bank for the transaction ) and be your own payment gateway.