This is similar to competing services on venmo and paypal. I believe they make money on:
1. The "float". The interest that they make from the period that people have cash in their accounts. If an ACH takes 4 days to complete, they may take 5 days to complete it, and collect a day's worth of interest
2. The halo effect. Now you're a Paypal/venmo/square user, and therefore more accessible to vendors using them as a payment processor. Those vendors pay the service transaction fees.
1. The "float". The interest that they make from the period that people have cash in their accounts. If an ACH takes 4 days to complete, they may take 5 days to complete it, and collect a day's worth of interest
2. The halo effect. Now you're a Paypal/venmo/square user, and therefore more accessible to vendors using them as a payment processor. Those vendors pay the service transaction fees.