[jasode]

>There are no cost other than hosting.

If one is trying to sell non-free software, it requires a payment processor like PayPal, Stripe, DigitalRiver, or paying a bank a monthly maintenance fee for a full-blown merchant account to accept credit-cards. A cursory google of Steam says they charge 5% fees for video games. They all have fees based on a percentage of the sales price. Even something outside of traditional payments infrastructure such as Bitcoin has fees.

If the cost is truly $0 like a sibling comment mentioned, how are people selling software for money without paying any fees to any intermediaries?

[cm2187]

Agreed. Add hosting and the fair cost is probably in the region of 7%. That's still very far from 30%.