You can read more about JET fees in JET Terms document. Below an example of an order and fees applied:
Items Base Price - price of an item, this is the price you specify on your product page
Shipping Cost - calculated based on your fulfillment node shipping settings
Base Fee - JET’s fee, usually 15%, calculates as: (Products Price + Shipping Cost) * 15%
Total Payable - how much a merchant will receive from JET for this order
GeekSeller fee is calculated from Total payable: (Total payable) * 1%. Please note that 1% GeekSeller’s fee in this case will be 9c ( $9.26 * 1% = $0.09 ). And this 9c will be paid by a merchant via Credit Card provided in GeekSeller billing section. The total payable are paid by JET to merchants.
Additional adjustments - a seller can also use JET Rules Engine to include additional adjustments / discounts.