This feature goes around the possibility to have a place where to calculate and charge "fees" to your end users.
Fees meaning, literally anything, for example:
A fixed amount for every X product or a percentage of Y sold product.
Here are some basic functionalities.
1) Fixed and percentage amounts
2) Associable to specific products.
3) Frequency (How many times it will be charged).
4) Exclusions. Exclude specific customers.