Information directly from Amazon:
“When a person outside of the US purchases an eBook on Amazon.com, he pays the price that is listed in the Kindle Store allocated to his country converted to USD.
A person from Australia purchases your book on Amazon.com.
When you chose to base your international prices on the US price, the conversion to different currencies takes place at the time you enter that price and does not change unless you re-enter the US price and hit “Save” again.”
“Unfortunately, we do not have a system in place that corrects the exchange rate on a constant basis.
With that in mind, in order to avoid such problems in the future, I would suggest manually entering a price for each Kindle Store rather than making all of the Kindle Stores have a “US-Based” price.
Alternatively, you can regularly re-enter your US price for the conversion rate to change.”
(Just to clarify the above: the ebook price was set at $5.99 US which converted automatically to $6.33 AU. However, when the ebook sold, the exchange rate was less advantageous so $6.33 AU converted to less than $5.99 US. Note: AU does not have an included VAT.)
The other issue you need to consider is that VAT is now INCLUDED in the price you set for your ebook. The % of VAT for a given EU country can be found on Amazon and if you had a previously published ebook you should have received an email regarding VAT. You will receive royalties for the price minus the included VAT. You should make sure you compensate for that in your pricing.
You can get today’s exchange rate at oanda.com. I think you can get previous days’ rates there too. That helps you check to see where you need to set your other country prices. If you have a good rate using the price you have set now you may not want to change them.
It can get complicated taking these things into consideration when setting or changing your ebook price. You may want to check the exchange rate periodically to keep your royalty return at the rate you are expecting. When you want to change your price, it will not take effect until you save it.
The one thing you do not want to do is be lazy and just tick that box thinking it mean what it says. It doesn’t any more.
Hopefully on LinkedIn some commenters may have better methods for monitoring rates and pricing. Cheers!