Various vendors may apply payment gateway integration fees. The most popular payment solutions need merchants to pay zero setup and monthly fees. However, businesses have to pay per-transaction fees that are the following: PayPal: 2.9% + $0.30 per transaction Stripe: 2.9% + $0.30 per transaction Amazon Pay: 2.9% + $0.30 per transaction Afterpay: $0 for on-time payments; 25% for late payments Braintree: 2.59% + $0.49 per transaction In case you hire software engineers to conduct the integration of the payment gateway, you will be required to cover extra labor force expenses.