What you shouldn't do is to hope that anyone will pay you.
The first person who pays can offer exactly the same thing for $0.
It's impossible to convince anyone that they should pay you even $1 if exactly the same thing is available for $0 from somewhere else.
The ability to charge for GPL software is purely theoretical. In practice, you can't.
Actually the majority of corporations are leechers, using it as "free beer", only paying back if they really have to, as many corporations don't use software without support contracts.
Or happen to have some FOSS followers taking business decisions.
Otherwise, I can tell you from my experience working on Fortune 500 consulting projects, very seldom is any money or contribution given back.
Radiohead's In Rainbows, the Humble Bundles and other pay-what-you-want sales disprove that statement. All had average purchase prices well above the minimum. (That doesn't mean such a model is very profitable compared to fixed prices, of course.)
Even in a purely self-interested point of view, there are reasons for paying (e.g. keeping development active).
Maybe so; can you point out those cases where the average payment for a pay-what-you-want sale was no higher than the absolute minimum?
hardly a model to follow for anyone that needs a steady source of income to pay things like mortgage, employees and such.
That's a very different claim from what I was contesting.
But in any case, it may work in when you have modest needs; Joey Hess just got his second year of development of Git-Annex funded[1]. Of course, not everyone is willing to work for $15k/year, even if it comes with few strings attached, particularly obviously talented and experienced developers like him.
That is the main point, in Germany you can earn around 5x that on an average consulting job.