The lines and general abysmal service at an actual brick & mortar USPost Office.
Someone also has to pay for currency conversion.
It's just a general hassle and not worth it on small items.
Go ahead and flame me.
I get inquiries from overseas here on apug from people that have just signed up or only a few posts if any.
I tend to be extremely leery of those but if an established apug subscriber and someone I know from participating in the forums wants something shipped internationally I will try to accommodate them.