Hi,
A little late to this thread but I'll put forward the information you need to know.
ALL Goods and Services coming INTO the UK are subject to Import Duty and VAT. The 'rates' at which they're charged vary depending on what it is. A massive and comprehensive listing of products is on the HMRC website. There's a threshold as mentioned above, if anything is lower than that figure it's exempt, anything more is subject to charges.
It doesn't matter if the item is new or used, it's still subject to the fees. Correctly marking what's in the package and paying the due charges is part of the UK's financial income. The temptation to undervalue items to avoid or reduce taxes chargeable is illegal and Customs Officers aren't stupid ! Everything is scanned and X rayed upon entry to the country.
When it comes to personal parcels, the above all applies still, however, a quick scan of what the declaration says, the weight of the parcel etc will 'flag up' things which might be incorrect. Else, it's processed, checked, scanned and charges added and sent on for the delivery chain. Items which have been mis-declared for the purposes of reducing or avoiding taxes get through all the time given the sheer volume of parcels/packets coming through but plenty are also intercepted and the correct amount of tax is applied and the recipient notified to pay prior to getting their items/goods.
The other way around and sending items TO the USA. This depends on which state it's going to and the state legislation on imports etc. They vary from state to state. Generally, there's no import duty coming into the USA, but I have read it can be applied.
There's no legal way of avoiding paying the charges and those who try will/often/do get caught.
I do quite a lot of Importing into the UK and cover this topic a lot on other forums where people post to say they've been 'ripped off'. They haven't! the legislation is available on the HMRC website! I'll soon be ramping up my exports as well. A lot of importation is of course done by companies and businesses and the 'costs' are added to the product for when it hits the 'retail' stage. Different countries have different levels of pricing from the manufacturers or the exporters sending the goods, and you've guessed it, the UK has some of the highest importation/buying levels in this regard - which is a big part of why the exact same product in the UK is quite a lot more expensive when directly compared to the the price in another country.
Cheers, DtM! West London & Slough UK!