Hmm, PayPal has an FAQ that says the below. But the FAQ also tells you where to get to a link to see their currency exchange rates, and there's no link visible where it tells you to go.
"We receive a wholesale rate quote from our bank twice a day and add 2.5% to determine the retail foreign exchange rate to apply to transactions that involve a currency conversion."
I guess we have to keep in mind this surcharge when price comparing between a Japanese store and a U.S. one. More of the damn eBay nickel-and-dime price gouging effect.
Paypal ALSO charges a 1% fee which they include so it's like 3.5% total. But it feels like more.