Or just start a company and make money from your code. The code can still be open source and if you really want to write free software then just do it when you have enough money.
That type of phrasing can also be used sarcastically or meanly, so people may have interpreted it that way. "Why can't you do this? Just make it work!"
But the original comment might also wrongly come from the perspective that a given developer ought to tie themselves to a particular project by creating a business around it. Many projects are created and/or maintained by developers working on a broad number of projects, so total productivity might decrease if developers were settle down with only one or two projects which they're able to build a business around.