Do you honestly think that this is going to stop with Skyrim?
There is both good, and bad in this.
First i already seen that steam pulled some of the "paid" mods, because of the issue of modders using others work, or IP without their permissions, or knowledge. It has already created the inevitable "shit storm", but i saw that coming.
That was what i was afraid of. That people would try to charge for mods that they didn't fully create themselves. Using plagiarized assets. Which is unleashing the copyright lawyers like hounds from hell. I will give you 3 guesses who will win in all this, but you will only need one.
If it is an authors own "original" art work, or "original IP" then i see no issue with charging for it. It is no different than a developer charging for their game. People will vote with their wallet whether its "good', or not.
It will encourage up, and coming artist.
You can chose "not" to charge for your work.
You can chose "not" to buy it.
You cant charge for a mod that is, and/or based on others work, or copyrighted IP.. For example Star Trek: SoA 2. The only reason Paramount lawyers are not spamming cease, and desist letters slamming the door shut on our mod is because we DO NOT charge for it. If that mod was my own original IP then hell yes i would be charging for it! It took me YEARS of sleepless nights, and tedious WORK to get it where it was before Psychoak, and Myfist0 took over the project. Where is my compensation? Answer is that there is no compensation, because it would be totally illegal. Being that Star Trek is copyrighted IP.
I could not charge for The Sins Optimization Project ether, because it would violate Stardock, and Ironclads EULA. In the end i was compensated, but in other ways
Same would be true "if" someone created a mod for Skyrim based on Lord of the Rings IP.
However, Original IP, Original Content, Original Art, and Original Code would all be fair to charge a "reasonable" price.
Counterstrike was a MOD, before it became a paid for add-on. Battlefield 2 on up wouldn't exist without the Desert Combat mod for BF 1942. The Sims, and Second Life community's charge for their content. So i am not at all surprised this has happened. It was not a question of "If", but "When" it will happen.
Free modding will still be as popular as always, because despite my previous statement i do love modding as a hobby. There are many others like me that feel the same way. Once you take that hobby away, and go professional, then modding become a "chore". Sure you may be paid for it, but then it becomes a tedious grind just to get something done. Much like mod burnout. The passion is gone, but you "must" finish, because you already have been paid to do so.