Steam price policy

Hi @ all

For example:

1. Command & Conquer: Red Alert 3
Steam price: 49,99€
Amazon.de price: 19,95€*

2. Mirror's Edge
Steam price: 49,99€
Amazon.de price: 18,90€*


What's the reason for this behavior. Okay, Steam has the weekend deal for a few games, but the price of the "big" games is the same since publication.
I would like to buy these games on Steam, but only for a current
Price.
And all this, after the EURO-changeover...