Visa, MasterCard and Discover make money by charging assessments on every transaction involving one of their credit cards. Like interchange, assessments are the same for all credit card processors and no processor can give you a lower rate or a better deal on assessments.
However, assessments may be charged differently if you have a bundled pricing model. Reason being is that your processor has more control to manipulate pricing on a bundled pricing system.
The assessments for each card brand are listed below along with the details about when they apply. Assessments are changed periodically by the card brands, and this list is updated as changes are announced.
The only true assessment fee from each card brand is the percentage charge applied to volume. The various other fees such as network access, foreign handling, and so forth are charges incurred through processing behavior at the individual transaction level. I refer to card brand charges collectively as assessments because these charges are consistent for all businesses.