I’m not really sure if this is considered a bug or an oversight, so I’m just going to place it here, if that’s alright!
Regarding the fee system in Airport CEO, one of them is always weirder than any other! And that happens to be the vending machine’s fee slider. All the other sliders have “stops” in them where the slider will snap to a certain point, usually for different numbers. (Example: Bathroom slider has stops for $1-$10) But the vending machine has no stops in between fee prices!
Because of this strange design flaw, you can actually set the price to a +2.5% markup on prices, and get both yellow and green acceptance levels as shown by the screenshots added!
Does this affect gameplay? Not in particular, but it seems very strange when compared to the rest of the fees.
Tested on October 14th, 2020
Tested on version beta 1-1.2 of the stable branch
Submitted bug report, ACEO-35297