Those are some great models and the price isn't too bad.
I am going to beat this drum again: If you want to sell an STL file show me pictures of prints and painted models. It's one thing to produce a great STL file that looks great when rendered by a computer. That doesn't mean it will print. Even with supports, etc, some shapes just do not print well. Sometimes there's so much support material that important surfaces are all scarred up by its removal. Sometimes the layers are more visible. Sometimes there is sagging, stringing, ghosting, warping, etc. The clever user can mitigate these with skill and time, depending on the printer, some STL files are much more prone to trouble and are much trickier to print.
Amazing things can be 3D printed, but the STL files have to be prepared properly. And rendered images do not reveal whether or not they've been prepared properly. When I see renders but not prints I am instantly suspicious.
I apologize to the folks who have to listen to this tirade repeatedly, but I think this is an important idea for advancing this side of our hobby. If you paid $50 USD for some STL files and spent five hours trying to print one vehicle and never got anything useful would you ever buy an STL file again?
Show us photos, not renders!
But those are good looking models (or renders, anyway), and I hope this campaign does great!