At one time, maybe that was true. But I doubt it. From the get-go, writers who are making a good living never allowed themselves to be underpaid. Instead, they just passed on the "opportunity," politely. Today, I did the same with an "opportunity" to significantly enhance my credentials ghostwriting about higher education.
However, it rarely is true now. There is simply too much turbulence in communications, all aspects of it. The business of writing demands that we only accept assignments which enable us to pay our bills. And a bird in the hand is always better than one in the bush.