Grading is marketing. If it isn't, what does it then say about the maker? Is the maker willing to sell sub par merchandise and are buyers willing to purchase subpar merchandise? There has to be a minimum standard of excellence that defines the products made by any individual maker. Once that standard is defined, assuming that it includes an excellent fit, finish, and quality of workmanship that is definable, the only other aspects worthy of impacting costs would be those controlled by the natural beauty of the wood - as in grain, difficulty of mastering the shape, time to complete, and I suppose, experience in perfecting a certain shape or finish at a level deemed only possible with extra labor.
Savinelli, Peterson, and other mass producers are willing to sell sub par merchandise and it is priced accordingly. Nothing wrong with that and often, it allows purchases of pipes that would not otherwise be possible for some people.
Artisans.... that is an all together different category. For example: If I buy a Jack Howell, I want to know that it is the pipe he intended it to be and not one bit less. And, if he could have improved upon it, why didn't he before he sold it to me?