It's because there have apparently been changes at Amazon's end - you can't set your region to check prices (when logged out) and even proxy services seem to be having an issue, although prices are now being returned based solely on your IP address, it seems (I think if you change your location, you do still get the price of that region, but some prices at amazon.com aren't being changed to match amazon.co.uk, that I checked, even for those logged in as UK customers).
I suspect they've made similar changes in the API (which places like ereaderiq have to use) and may not be returning any pricing info for any region other than the IP address that sends in the query.
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