Are you based in the UK?
I know Amazon show the price based on what it is in your country and convert it based on the exchange rate. This scared me at first because I set my book to £3.99 and $3.99 but it was showing as a higher price when I viewed the US website. But when I asked someone in the US to view it, it showed the price as $3.99.
I'm having the opposite problem. I had a sale on my book for a few weeks and put it down to 99c. Now I've changed the price to 2.99 but it's still showing as 99c.