Patrick actually answers this point. The shorter is that while people are free to spend as they please to charities, businesses usually don't. He goes on to note that businesses have very different value structures. This means that while I may consider a hundred buck real money, an enterprise business very likely will not. The final bit is that businesses value some things disproportionately highly compared to the trivial cost of it. There are plenty of reasons for this that he makes clear.

But that value is for that service, not a charity. It will never get redirected otherwise. So getting a business to happily pay a large sum for a cheap service is a fantastic way to ensure you now have the money to donate, and likely an order of magnitude more.

This is also the reason he says to charge $500 a month, but to give away the service to them that need it. Because the business is effectively subsidizing the needy here, while itself provably working in it's own interest. This is pretty win-win if anything.