When you make a bitcoin transaction, you are sending funds to a bitcoin wallet address controlled by another person. When you pay a BitPay invoice, that other person is BitPay. An Unspent Transaction Output (UTXO) is the payment a wallet receives and then transfers away from the receiving bitcoin address. This is the unit of bitcoin which a wallet can then actually use in another bitcoin transaction.
The extra network cost in your total invoice covers BitPay's cost to do a UTXO sweep for your payment. You can learn more about the reasons for this extra fee here: https://blog.bitpay.com/network-costs/
Didn't I already pay my miner fee?
The cost for BitPay to do a UTXO sweep is different from the miner fee you also paid. Your own miner fee helps determines how fast your payment will confirm on the bitcoin network. This is a function of the Bitcoin network. BitPay can NOT control confirmation times on the bitcoin network. To learn more about bitcoin miner fees, click here.
How can I reduce this cost?
If you want to reduce extra network costs on your BitPay payments, we recommend making bitcoin purchases in larger groups. This will offset the cost across a larger value. So instead of making ten $10 payments, try to make two $50 payments or one $100 payment.
For any extra payments you have to make to the BitPay invoice, BitPay will add them to the network cost. To avoid paying the network cost twice, be sure to pay the exact BTC amount requested on the BitPay invoice. To make sure you don't overpay or underpay, scan the QR code on the BitPay invoice. We also recommend paying with a payment-protocol compatible wallet like the BitPay app.