ONE absolute truth
There are some parts in your "absolute truth" that are well-known to be self-contradictory.
For example, GPL in all forms explicitly protects your freedom to sell copies of software
. Because if you restrict that, it'd be a restriction, and you said "no restrictions of any kind on distribution"
NoQ, you are right again, they can try to sell it, but they are also obligated to make it available for free if they modify it or improve it in any way, shape or form.
So, if the exact same thing is largely available for free, who's gonna buy it???
Maybe some people will, for various reasons, one of them being to support the people creating and modifying it...
As an example: While I did see eBay listings selling Live DVD versions of Linux, and there are people out there that are actually buying them, you can also download the exact same version of Linux for free.