I think you're thinking marginal costs. Only charging for marginal costs will put you out of business almost immediately. There are plenty of non-marginal costs that need to be covered, which will make it "not close to $0".

If you think I'm talking nonsense, make sure you know what the term actually means: https://www.investopedia.com/terms/m/marginalcostofproductio... There's a common misuse (unless it has become so common that it's just another definition, if you're a descriptivist grammarian) to use it to mean "small, negligible", but I'm using it in the real business/accounting sense. Of all the industries, tech is among the worst in terms of being unable to charge based on marginal costs; so often our marginal costs are effectively $0 but the fixed costs of what we have are millions to billions of dollars.