Sure, but for anyone who doesn't have the knowledge to assess, being willing to shell out a sum of money for the change to evaluate it is dependent on believing there is something about the individual that will make him a decent candidate to possess good knowledge or have access to expertise we don't.
If he is an elite competitor, or coaches elite competitors, or has a significant research background, one has a prima facie case that the person knows something of significance to convey. If someone has a research background comparable to Mel Sif, or is an olympic athlete, they probably know some stuff about elite power training I don't.
If someone without that background says they have some awesome training info, I will need lots of good reviews from critical sources before I'm not an idiot to buy their product.