Merchant credit services charge various per-transaction fees and offer monthly subscription programs. The most common cost is the interchange rate. Credit cards like Visa charge this fee, and it gets passed to you.  Most processors use an interchange-plus pricing model. This fee includes a percentage of your sale that goes to the processor and a rate per payment fee. Prices vary by company but typically have the following ranges:  Monthly fees: $0 to $599 per month Transaction fees: 0% to 3.5% per payment Flat-rate fees: $0.05 to $0.30 per transaction