Valve is where they are at because Gabe knows he is rich enough and doesn't need to squeeze every penny out of their customers' pocket, nor is there any investors making him do so. Maximizing the price of the steam machine which is already going way above the anticipated price due to component prices skyrocketing will be perceived as a giant fuck you move and burn years of goodwill, erasing a major competitive advantage valve holds over other game storefronts.