As you can see, it is normal. For some reason a LOT of Blu-rays are cheaper in the UK, so you're better off looking at Amazon's UK website before ordering in the US. Your login details and payment details are the same as the US website. Also VAT (sales tax) of 20% will be taken off at the payment screen as you reside outside the EU. They even write "Region Free" in the title of a lot of Blu-rays. Some deals I bought recently on the UK website:
Superman Anthology - £24.99 with VAT (about $39) vs. Superman: The Motion Picture Anthology, 1978-2006 [Blu-ray]
Harry Potter 8 Film Set - £32.30 with VAT (about $51) vs. Harry Potter: The Complete Collection Years 1-7 [Blu-ray]
Alien Anthology - £13.99 with VAT (about $22) vs. Alien Anthology [Blu-ray]
The Pacific / Band of Brothers - Limited Edition Gift Set - £36.47 with VAT (about $57) vs. Band of Brothers / The Pacific (Special Edition Gift Set) [Blu-ray]
If on the other hand if you don't want age rating logos and other languages printed on your packaging and discs keep buying the USA versions. The only one laughing all the way to the bank are the film companies with your hard-earned extra dollars.