Seems to me thereâ€™s two separate issues here â€“ first is customs do sometimes make mistakes like everyone else, second is that nobody likes paying taxes so everybody starts looking for illegal ways to avoid it. Combine the two and you can get all manner of myths becoming the accepted wisdom.
If you have to pay a very high percentage, you may have been overcharged so you need to (politely!) seek an explanation of the charge, which may reveal an error, which they might correct with a refund. Trouble is most ppl are so angry and disgusted, they donâ€™t bother to get an explanation. But if youâ€™ve been charged 16% duty on a frame, thatâ€™s just a mistake, should be 5%(?) on parts, should be possible to get that corrected if the invoice is clear.
The trouble with evasion is that lying could get you into trouble and it entails asking your seller to tell an equivalent whopper, and why should they? Businesses by and large wonâ€™t take risks for your sake. Anyway, â€˜giftâ€™ doesnâ€™t get you very far, as the limit is only Â£30ish, and â€˜repairâ€™ and â€˜warrantyâ€™ carry the risk of being required to prove that you exported the thing to the seller previously. And I believe if you get a private seller to state a lower price than you paid, customs can charge duty on their own figure - what they think is a valid price.
I may be the odd one out here, but I donâ€™t object to paying import duty and VAT, itâ€™s always been like that, itâ€™s just that theyâ€™ve tightened up on it. I just plan for it, and then usually decide the US price isnâ€™t cheap after all. But ppl donâ€™t like nasty surprises, so before you buy you need to plan what you have to expect to pay â€“ i.e., to cheap-looking goods add hefty shipping/insurance, plus rip-off handling charge, plus correct rate of duty on all the aforementioned and then 17.5% VAT on all the aforementioned. Can easily add 50%, which certainly comes into the category â€˜nasty surprisesâ€™ if you didnâ€™t plan for it.