First we must make it clear that imposing additional fees for the usage of a particular payment gateway is not legal in some countries. Moreover for some payment gateways this practice constitutes a breach of the contract. That being said, make your considerations before you start using this option.
All applied fees are effective in the sense that Payments Bundle uses a formula that guarantees you to receive the exact amount of the invoice. Let us give you an example. The fees of a specific gateways are 3.4% plus 0.35 euro and the total of the invoice is 100 euro.
Intuitively the fees of the invoice should be 3.4% + 0.35 of 100 therefore 3.75 euro but it would not be correct. The result would be 103.75 euro on which the gateway still charges 3.4% + 0.35 giving you the following outcome:
- Total: 103.75 euro
- Fees: 3.88
- Income: 103.75 - 3.8 = 99.87 euro
As you can see in the process it's true that you saved 3.75 euro but you are still losing 0.13 euro. That's why the module uses a formula that adjusts the fee so that you are guaranteed to receive exacly 100 euro.