This is when people would just re-create the mod and release it for free.
Or a free add-on hosting service, which a lot more people would use.
Also, this whole idea is bullstuff. I can understand donating for small cool extra things in the server like a different shirt color or weapon or something for a SMALL donation, and not bringing you an unfair advantage over other players in the process.
But add-ons costing money? Go back to roblox.