No. Sorry. That model is bullshit.
I dont care how much the developer thinks it is worth, or how entitled to royalties they feel they are. The effort that goes into many mods rivals the effort the original studio put in, and in some cases greatly exceeds it. It boils down to "We put our flag down first, so pay us forever."
In my not so honest opinion, that is one of the things that is currently very wrong with the world. Everyone wants to extort from everyone else, and nobody wants to contribute to the public common, even though a thriving public common is what creates culture. You end up with the likes of Disney and pals, who fight tooth and nail to keep works out of the common for centuries, because "MY CREATIVE CONTENT! IT'S MINE! MINE I SAY! YOU HAVE TO PAY FOR THAT BECAUSE I SAID SO!"
I will again (as I participated in round one of this thread) point out, that many of the tools, techniques, and assets used in mods cross proliferate, because the mod community operates (predominantly) on the public commons model. That means work only needs to be done once, and all later comers can gain use of that work, to build better, more elaborate works.
It is only in the "NO! YOU MUST PAY ME *FOREVER AND EVER AND EVER!!*" model that work must be constantly re-done, with conspicuous effort invested to PROVE that it is different from those other works created before (and thus does not violate some 'property right') that you end up with recurring, and exponentially increasing costs in the creative process.
It costs AAA studios so fucking much money, because they are all shouting
"MINE MINE MINE!" all the damned time, and so are constantly reinventing the wheel.
And, to head some hotheads off at the pass-- No, I am not saying you should work for free. The method of payment you get just isn't in cash. What you get in exchange for a novel tool, is works created using that tool suddenly appearing in the community. You give up the fruit of your creativity, and get the fruits of hundreds of other people's creativity in return. Other people will improve your tool, or your asset, and the status of the commons improves. You see this everywhere.
For a pretty high powered example:
What did Linus Torvalds get from making his linux kernel FOSS?
Android phones
Inexpensive home routers
Inexpensive home NAS boxes
Dozens of linux desktop and server distributions
Smart devices of all shapes and sizes
LOTS of software targeted at the platform, for any purpose imaginable.
If you added up the market value of all of those later innovations that are directly tied to his contribution to the common (which he had to protect with the GPL, to KEEP it in the common) it will greatly exceed what even a very skilled business mogul could have spun from it.
You will find that this is true with ANY novel innovation that goes into the common. A rising tide raises all ships.
When somebody decides that they want to raise their ship higher, by pumping out the water into a closed pool, (which is what exclusive licensing, and all that noise equates to metaphorically) you dont get that effect anymore. It then becomes less about raising one's own boat, it is about assuring the other boats SINK.
So NO. Paid mods are bad. Always.