In LissAngel we have no minimum order, that is, you can buy the product with the lowest price you want and nothing else. If for example you buy a pen that costs to you € 0.80 and you decide to pay with PayPal, PayPal charges us for selling that pen € 0.35 + 3.5%, that is € 0.38 of commissions.
In that example, we simply do not gain anything, and we even lose money. For that reason, we have put a small commission for payment by PayPal.
Naturally, our other two payment methods (bank card and transfer) do not have any commission on our part.
Why other stores do not have a commission for paying with Paypal?
Simply because they have minimum order, or do not sell products at very low prices, which will have more margin.