We paid for a service through paypal . The seller is now asking us to pay for the fee. What is the halacha?

Question clarified:

We paid for a service through Paypal and were advised to send payment as friends to avoid the transaction fee. This option was not available and we had to make the payment right away so we sent it through regular PayPal. The seller is now asking us to pay for the fee. According to Paypal, the seller is responsible for the fee. What is the halachic view on this?



Disclaimer: the following discusses the halachic components, not the legal ones.
If the seller – or service provider – didn’t stipulate anything in advance, the fee would be on the buyer, as per the PayPal guidelines. If he stipulated to avoid the fee and the buyer made the transaction with the fee, the fee is on the buyer. In other words the price was minus the fee. Had the seller intended to pay the fee, the price would have been higher to include it.
(There is no aspect of ribbis in this case [See Beis Efraim Y.D. 41.Mayim Rabim 38. Mishpat Ribis 20:8. Bris Yehuda ch. 22 fn. 6].)
In this case where there was a specific request to pay as a “friend” it is equivalent to a stipulation. On the other hand, it appears from your account that there was a request to submit the funds right away regardless of the stipulation. This matter requires further clarification.
The Halachah is that a Dayan (a judge in a Beis Din) may not listen to one litigant in a Choshen Mishpat (financial) dispute unless the other litigant is present—ze bifnei ze. Thus, we cannot provide a definitive answer in this case.
Thank you for your understanding.