Its not Valve, it is the game developers. They set the prices, not Valve (unless it is a Valve title). TWI stated this, and priced RO2 the same in all regions (with included VAT). Most game devs just "covert" $60 into 60 Euros, ect. In the end, it is up to the independent game devs/publishers.
Autodesk does this with 3D studio max as well. $3,500 USD = 3,500 Euros on their website.