Oh, do you mean like 3rd party companies selling their mod for a price...?
No. I mean like in the "old days" of modding people just made mods out of ideas they thought would be fun. No one was concerned with the graphics and everything was just like different colored skins on the game objects. Capture the Flag started in Q1 as a mod, and the flags were the silver and gold keys. It didn't matter, they wanted CTF and released it as quickly as they could and then evolved it later (by adding real flag models). We also had stuff like the grappling hook, runes, Rocket Arena...just stuff that diidnt have a lot of new content and was all about trying new ideas. Quake Rally, Quess (chess in Quake), and other kind of "out there" ideas were fine. Mods were made by one person or at most a small team.
Since CS got popular, that all changed. Now everyone makes mods with bog standard gameplay so its popular. They don't really try to do anything new. They hire large teams to work on the models/maps/textures to make it pretty. They hold the release back longer and longer to make it a "professional" release. So what you end up with is a nice looking mod with standard or crappy gameplay that gets one release and is never touched again.
The trick to mods: release early, release often. Be concerned with your gameplay. Get it out there to the players, get feedback, tweak as necessary. Once you've got the gameplay down, now you can go in and throw on those layers of polish, the textures, the models, etc. When you're done you will have a nice looking mod with well tested gameplay that the players like and a playerbase/community that you built up over time.