Yeah, I mean about the only kind of Mod I'd pay for would be ones that are pretty much expansion packs. I'm not going to pay for some random item.
Also, I do think if a modder is going to try and sell a mod they need approval from the original developers, since technically that's the only legal way to sell them and it's just the right thing to do.
Also, did you guys know some people were trying to sell Project Brazil as a hard copy expansion of FNV? The devs of the Mod were unaware for a while apparently, and I think they've(along with bethesda probably) shut it down since.