Not only in NL. Same thing with different titles from JP too. I have started seeing this a few months ago.
There are two easy way to compare the intended and local price:
1. Put the book into your wishlist.
2. Click the "See all X formats and editions" option. You will see the intended US price)
Now, I could understand an addition dollar or two as "international tax", but double price?
(Interestingly, while I have no data to back it up, it looks like that less book have the Whispersync (ebook plus audio) option if you access the site from a non-US location.)
Here is an example: