This would be true if FDev attempted to charge for player-made content. But that's not how it would work.The legal issues across various countries and the managing of said content would be a nightmare.
FDev would charge for the tools to create content. Players who made content and submitted it for inclusion in the game would thereby be waiving their rights to payment for the items submitted, and FDev would include the items without further charge to players, having made their money from selling the tools.
Years ago I used to play an FPS by id called Quake III Arena. The game only shipped with about twenty playable arenas (maps or levels). But it also shipped with a map editor: people used this to make new levels which they then made then made available for download. By the time I stopped playing I had a collection of over two and a half thousand levels, most of them as good as or better than id's original offerings.
We'd have a much livelier galaxy to play in if we could get even a fraction of that kind of community design contribution going for Elite Dangerous.