Hi. Emmanuel @ Airfordable here. Thanks for the feedback and we'll work on making the fee more prominent. Just in case you missed it, we do have our fee on the site in the FAQ's and on our home page.
It seems like you're gauging your customers. Assuming you book 3 months out, that's a 40% interest rate (or so). It's quite sad the most vulnerable would be stuck paying that instead of a credit card loan for 3 months.