Why electronic products are so expensive in US or UK?

I mean, for example, the exactly same wireless keyboard from Logitech,

• it's around £40 in UK, see it on Logitech official website, and about the same on Amazon UK.
• but only £20 in China, see it on JD.com (i.e. the China version of Amazon Prime).

And I also think, the US/UK gov wouldn't allow the China vendor to sell the same products in their markets, because that would bring down the price significantly, right?

I really don't understand why the price could be so much higher in US or UK, any comments are more than welcome!

Thanks