i don't think they called it surcharge, but just different way fx are calculated. i suspect when you choose pay later, fx conversion will not be handled by agoda, perhaps by the hotel? just making guesses here.
i think they could have explain it better
Pay Now bookings
When you select your Payment Currency on the booking page, we will update your total price to show the amount we will process to your payment account. We can do this because we know the exchange rate at that time. Agoda uses our Indicated Rate to convert currencies for Pay Now transactions.
Book Now Pay Later bookings
When you select your Payment Currency on the booking page, we will update your total price to show an estimate of the amount we will process on your payment date. We cannot show you the exact amount because the exchange rate will fluctuate between the booking date and the payment date. Agoda uses our Daily Adjusted Rate for Book Now Pay Later transactions.
Indicated Rate – Bloomberg Generic Composite Rate mid-rate on the current day.
Daily Adjusted Rate – Bloomberg Generic Composite Rate on the day payment is processed plus 5%.
When you choose to have Agoda handle the currency conversion on the transaction, we will not charge you an additional transaction or service fee.
Obviously u can’t put the entire t&c out, but to inform the 5% surcharge, how difficult is it? If they can write “subject to exchange rate fluctuations”, I don’t see why they can’t add “5% surcharge”? Duhhhhhh