Larian Studios Forums Divinity - Original Sin Divinity Original Sin - Mods Mods for sale, with official support ?

That is not true. In fact, the opposite is more likely.
People will see an easy way to make money and use the least amount of effort possible. Hey presto, mods that cost, but don't add a lot!
Now let's look at how modding communities are for games that are still open to modding, these days:
Modder enjoys game, enjoys modding.
Modder puts in time and effort to create something, shares it with the rest of the world.
Modder feels happy his work is enjoyed by others and continues to provide support through fixes or expansion.

Now, someone who made some easy cash will never put in more effort than they feel is 'justified' by their earnings.
You can see this happening on developer level these days. Just look at EA/Battlefield or the high amount of unfinished early access or beta games, even if the latter somehow got gold status. (Released as full game but is obviously lacking a lot.)