I've not ordered specifically from them but I do have a number of international suppliers where I really have to watch how much I order at any one time. Simply because of the horrendous duties that need to be paid if I'm over the limit.
When ordering anything from outside of your own country there is always the possibility that you will need to pay import duties, just as when you ship to another country your buyer needs to be aware of any import duties that they may need to pay.