Richard, I don't know whether some of the posts have not arrived at or been deleted from your server, but if you have all the mesages I can see and you made the effort to read them, it has been stated at least twice that, while tax is levied at every stage, there is a refund at every stage except at the end.
Thus X% tax means X% tax, not some compounded figure.
The reasons for the higher prices for certain items in Europe vary across the items and across countries.
To take one specific example where I did some research a while ago: a fairly decent Canon SLR camera. I checked in Singapore (very low sales tax) and in two places in the USA. The two places were quite different and the dearer one was within shouting distance of the UK. Singapore was lower approx by the VAT amount, which makes sense. Still wasn't worthwhile because of potential warranty issues. I also checked out an expensive lens at Singapore airport. Cheaper in UK because, presumably, the volume for this item was low at the airport.
Another one was a computer printer I (almost) bought in NYC. I needed a small printer while visiting New York a couple of years ago or so. As I had an afternoon free I thought I would potter down to the nearest computer superstore (Compusa, was it?) and maybe even save some money cf UK. To cut a long story short, by the time the manufacturer's international warranty was added the price was similar to the UK's (where we get international warranties on many items -- e.g. my new Toshiba M100 notebook -- 3 years anywhere, rather useful as I travel quite a lot, also outside the old EU countries -- EU border moved east on May 1).
But on another occasion I took a chance and bought a video recorder at Dubai (no European guarantee) -- that was a bargain cf UK and has worked perfectly for years, admittedly at low levels of use.
DAS