Hello,
I called Airbnb Payments UK Ltd +44 2033181111 because I am experiencing a similar issue.
I have a property in Spain that I set it up in Euros as payment method for my guests (I thought it will make easier for guests to book and compare with similar properties around the area and avoid fluctuation on exchange rates) although my paypal account is UK based as I am a UK resident.
Unfortunately this was a mistake for me as Airbnb terms and conditions estates that when the payout currency differs from the payment currency then the money will be exchange to $ (US dollars), then Airbnb will charge a 3% for exchanging back to the payout currency. So the Euro payment taken by Airbnb is exchanged to Dollars and when the guest arrives to my place those Dollars are exchanged to Pounds (not sure what exchange rate they take, current or the original when the payment was taken, plus obviously the 3%).
I am currently seeking advice and waiting for a reply from Airbnb on this methodology as reviewing payments from them to me in Pounds and comparing with the original Euro payment as sometimes the fee taken has reach well over the 3% stated on their terms and conditions.
I will recommend to call them and hopefully if more of us are having the same issue and complaint they will try to make more transparent and fair theirs terms and conditions.
I hope everything explained previously makes sense as it took me a while to make sense of it myself.