Customs duties seem to be a real nightmare. From what Wompet says they are applied in a particularly arbitrary way and there is no form of guidance you can try to price things beforehand. There is also possibly an element of protectionism to discourage imports but when there doesn't seem to be any significant indigenous manufacture of tartan to protect it is hard to justify. The fact remains, however, that it is bound to discriminate against Scottish goods and it makes perfect sense for people to buy local as a result. Whether it is right or not is another matter altogether.