Estimate travel booking fees.
Booking fees stack in a specific order, and the order changes the total. A percentage agency fee applies to the fare, a flat service fee applies per traveller, and the card surcharge applies to everything above it — so the surcharge is levied on the other fees as well as on the fare. That compounding is why a headline 3.5% agency fee plus a 1.8% card charge produces more than 5.3% in practice. The share-of-fare figure is what makes booking channels comparable, since each structures its fees differently.
Travel booking fees
Per traveller = fare x (1 + agency fee %) + flat fee; total = per traveller x travellers x (1 + card surcharge %)
They are banned on consumer cards in the UK and EU but remain common elsewhere and on commercial cards. Where permitted, paying by bank transfer or debit card frequently avoids them entirely.
Usually on fees, though not always on fare. Airlines and hotels rarely charge agency or service fees, but agencies sometimes hold negotiated fares that more than offset their fees — compare the total payable rather than either component.
Because it does not scale. A twelve-unit service fee is 2.5% of a 480 fare and 12% of a 100 one, which is why low-cost bookings are where flat fees do the most damage.