How do you distinguish a nonsense model from a good model when you don't have a writeup, you don't have validation data, and it is not possible to run cheap exp

How do you distinguish a nonsense model from a good model when you don't have a writeup, you don't have validation data, and it is not possible to run cheap experiments? I'm not saying you can't make money selling an RNG with a slick UI, you certainly can.