Costs are slightly lower than sales, I would expect. It's also a political issue when it comes to Humble Bundles and crowdfunding. Costs have dropped with C++1

Costs are slightly lower than sales, I would expect. It's also a political issue when it comes to Humble Bundles and crowdfunding. Costs have dropped with C++11, Unity and Steam for Linux. Sales have risen since Linux' market share is rising (very very slowly). Also of note is that Linux users seem to have beefier setups than their Windows peers, according to Steam Survey (12GB RAM vs 8, 2GB VRAM vs 1, bigger screens and more cores). More money spent on hardware correlates with more money being spent on games.