Last week the price comparison site Luzme calculated which are the most profitable eBook prices in the US and in the UK. While in the US the profit peak was around 9 to 10 Dollars, in the UK it was below 1 Pound.
Germany is different from both. I analyzed data from my Amazon-Top-1000-Tool that is now online since six months. It collected around 180.000 datasets on eBooks from the Amazon Top 1000.
The result for the units sold is not really surprising if you follow the Amazon charts in Germany as closely as me: eBooks sell best at 3.99 Euro and 2.99