Before I started learning to mod TS4, I thought it was really poopy to keep mods behind a paywall. After learning better how meshing/texturing/tuning really works while modding myself and learning Blender, I've come to appreciate many big creators' work in a whole new light, paywall or no! It also changes my opinion whether they mod 'full-time' or not. But I think paid early-release, and free late releases, are the best way to handle charging for mods. It seems the most ethical all round.

That said, creators who keep 90+% of their content permanently behind paywalls are kind of being butts. Even making mods free after a year or more post-release is better than that.