I meant market in the real sense not the American polemical form.
A real market-driven price/cut is determined by supply and demand, the 30% figure was chosen by some American oligarchs that Valve decided to copy.
Have you ever wondered why it's not 29.1% or 34.5% and the 30% figure never changes (other than than for well connected insiders?). How can market driven price never change, especially in a highly dynamic globalized market like gaming?