Besides the fact that you're pulling the "pay for mods" thing completely out of your ass, all of the consequences are the result of the modder's choices, not the developer/publisher.
Yes, because such things are totally unheard of elsewhere, aren't they? I'm sure Bethesda, just as any other
good company, never ever would come up with the idea of checking out what others do, what works and what
does not work in your own market. Then if it works, if money can be made, they themselves wouldn't even for
a second consider to implement anything of the sort in their own ways.
...and I said an example of what could happen...and I never said it was not the modder's choice if this would
come through whether to sell, or not. However, who's choice, if it happens, who is going to pay for it I think
we can agree on, is without doubt.