Come on -- you know as well as I what the clarification that makes the examples you listed legal is: Fair use (or fair dealing in other jurisdictions). Leaving aside that little bit of snark, the point is that a derivative work has multiple copyright holders. You don't dispute that.
I'm not sure what "to the extent that you have copyright on the result, it's due to your contribution" even means. What "result" -- the derivative work? What "contribution", exactly? The specific lines of code that were not present before? What about lines that were modified (say by changing a "==" to "!=")? Whose "contribution" are they?
The reason you can't charge for a distribution license on the derivative (not "resulting" -- it's a work derived from the existing work, which you were allowed to derive from (and copy, and distribute, etc.) by following the terms of the GPL) work is that you are not the sole copyright holder for it. If you get the agreement of all the copyright holders, you all can certainly refuse to grant additional licenses without payment.