The current version of MyCostPro calls it "Paypal fee." We are about to update it to read "Payment Processing Fee" or something to make it more generic. If you have opted into eBay's new manages payments program, it's their Adyen processing fee. For everyone else, it's the fee paid to PayPal for payment processing. Upgrade fee is the promoted listing fee, and various listing upgrades such as bold text, picture pack, etc. Hope this helps!
edit (scott): added a few more examples of Upgrade Fees