I actually do know what I'm talking about. See https://www.gnu.org/philosophy/selling.en.html

Many people believe that the spirit of the GNU Project is that you should not charge money for distributing copies of software, or that you should charge as little as possible—just enough to cover the cost. This is a misunderstanding.

Though I advise you to read the whole article. They for example explain why you should charge "substantial fee" for redistribution of Free Software.