Duty on imported kilts

[Bugbear]

I just can't see how I would deal with a sudden hundred plus dollar charge on something that seems to be at the whim of an inspector when I have had to budget buying the item so closely in the first place. Are they just pulling the amount charged out of the air?

It's not that paying the duty bothers me, but how do you know what the charge is going to be before you buy something... Hard to do business that way.