Certainly that sort of thing is ultimately what killed Paradox's paid mod-DLC idea.
When money enters the equation, customers start demanding more support, and modders might not be willing/able to provide that support. Moreover, there's a certain expectation for mods when they're paid vs unpaid - 'you get what you pay for' basically. Patches will very often break mods, and most modders aren't hugely professional (if they were they'd be game devs), so it's a crapshoot as to whether they'll update their mod for the new patch instead of wandering off. This leads to a fragmented and stagnating mod community. Veteran modders in paid mod communities are actively disincentivized from teaching newbies because newbies are potential competition.
Paid modding encourages mod communities to jealously hoard their content, code, and ideas because they can make money off of it. New modders generally learn the ropes by asking veteran modders how to do things. Basically, modding communities benefit immensely from open sharing of content, code, and ideas within that community.
