I handled a cast from the sweetwater biface yesterday. The original point sold for 150K!!! There is some large coins in the authentic artifact business.
The first thing one must do after finding and artifact is to get the point authenticated,papered if you will. Those that perform this, have ways and means of telling if a point is original, or if it is newly made and yes there are those who have mastered the art of deception with patina techniques. Trust me, they can tell. Once it is papered then if you choose to sell it, it can be put on the market.
People argue the fact that you have to paper your points, but the market has driven it in that direction.