I was considering purchasing a watch from the USA as it would appear to be a good bit cheaper than here. I would be grateful for any advise on any drawbacks, such as import duties etc. Thanks.
First thing, US prices are shown without any taxes (State or National) so you should add about 15 - 20% to get a proper comparison. US taxes are added at the time of sale. If you are buying US goods to be sent to the UK, UK VAT will be added instead of US taxes either by the US retailer or when it is imported into the UK. In addition there may be duty collectable on the watch you are buying. You should check with UK customs
In most cases and especially on Ebay, there is no tax added, since the U.S. has no National Sales Tax or VAT. Many States do have sales taxes probably averaging 5% to 6%, but they (for the present) aren't allowed to charge that if the sale is on an inter-sate or international basis...