Considering the at least 200+ hours I invested in give or take ten* games throughout my childhood / adolescence / young adult past, then even €100 would've been a steal.
I've always thought games were expensive until studying game development in college. From programming to 3D modeling, and boy can I confirm that it takes a lot of work to do well. The developers and artists that do it well, and ethically, deserve to be fairly compensated as such, provided no one becomes disproportionately rich.
*Age of Empires 2, MU Online, Unreal Tournament 1999/2004, Tony Hawk Pro Skater 1/2/3, Battlefield 1942, Wolfenstein: Enemy Territory, R.O.S.E. Online, Counter-Strike 1.6, Counter-Strike: Source, Battlefield 2, Insurgency.