What is the interval of 2 transaction and also please specify the amount you sent on both transaction. Bitpay always used the normal miner fee at the time you send the transaction. The fee is normal in BTC currency but due to rapid increase to price of BTC. The fee seems so high if you view it in fiat.
In electrum, it charge around 117.2sat/byte for 2 blocks which is around 4$. Maybe you send transaction by the time BTC network was clogged by pending transaction.
I tried it many times during the day and all the times it was showing high transaction fees. I was afraid I'd lose the items and hence went in for the sale.
Bitcoin is great. No doubt about that. But my apprehensions remain. All of this with Bitcoin is as confusing as the banking laws that very few of us understand.