The Diaper Movie, Steam takes it's 30% of each sale.
So if $5 is your 100% revenue, then Steam will take $1.5 per pop.
And you get $3.5, I'm not mentioning taxes you have to pay, because they are different in different countries.
Also, Steam only sends out a minimum of $100 (because of payment processing fees). So if you game makes say $35 a month it will take 3 months to receive your money.
Like it or not - that's how it works. Other game distribution platforms operate in approximately the same way. That information from above is all over the internet and developers all over the world are "not so" happy about it for years.