Considering the amount of time these people put in to the models, I would be amazed if they did it for free. Hell if someone made a supersweet model for my team, I´d pay them for their work whether they wanted it or not. Having but it that much time and with that amount of talent it is certainly worth some money.
High quality tracks is the same thing. The talent and work required for the good tracks are also worth paying for. Especially considering all the shit they get from the community.
From my point of view, there are two cases:
One is where a team owner or privateer asks a modeler, skinner or trackbuilder to make something for them. Custom made and the person basically "hires" the skinner/modeler. This is IMO ok to charge a fee for.
The other beeing someone just making a random thing for the sake of doing it. Maybe a skin or a track they wanted to do or a model they worked on in their freetime. This should never cost money IMO.
The big stupid part of all this is the really terrible folks out the trying to charge 1-5 dollars for skins and stuff. 95% of these are just not good enough to charge anything and should just create and release as many things as it takes for them to be good.
Now I can agree that paying a 100$ for a model that 99% of the people you race with will never see it kinda dumb. With the time they put into it its probably a really low hourly pay but thats just the thing, you cant charge that much for something like that and you´ve put way too much time into it.
Does the community really need a new model every year even tho the real bike barely changed? Nobody in the game will notice the difference.
If when a new bike model comes out, the modelers come together and during their free time the create this new model and pay a SMALL fee for it?
Ultimately, its the demand that makes it a little bit silly and Its beyond me that someone would pay 100$ for say a KTM model that looks almost exactly like the old one.
But in the end, its not hard just to ignore it altogether. If you dont want wanna pay 100$ for it, then dont. Just use the older models, nobody will notice the difference.
If there was a system in place that whatever skins and models you were using showed up in game for all the other players somehow it might be a little more worth, but that isnt in the game and it doesn't look like it ever will be so