If he says he'll wash your car, would you deny him the use of your garden hose?
Setting aside NGTM-1R's excellent point, Mobius didn't offer to wash my car. He shows up offering something unspecified, but demands payment before he'll provide it to us or even tell us what it is. Usually that form of negotiating indicates a scam.
Now we can speculate that he might be doing something cool with the model files that he will subsequently post in this thread, but that's just it -- speculating.