I received a message from Apple today, in response to an earlier post of mine. I've reproduced it bellow:

Hello

Your assumptions on UK VAT are correct; the iTunes Store sales prices 
in the United Kingdom are VAT (Value Added Tax) inclusive, as are any 
other goods sold in the UK. This is required by law, not by Apple policy. 
You can refer to the government tax website www.hmrc.gov.uk for an 
understanding of VAT laws. Every customer in the UK expects that VAT 
is included in their price, so this is not unusual for them.

To the contrary, USA customers are used to seeing sales taxes added at 
the time of checkout, and not included in the sales price of an item. This 
is how the iTunes Store reflects taxes - the same way customers are 
accustomed to seeing it as they would in any other store in the USA.

This is address in the FAQs on iTunes Connect, as well as explained in 
detail to anyone who emails iTStax@apple.com.

Kind regards,
[redacted]
iTunes Royalty Accounting