I reckon Mamady designed the proportions.
Jeramy found the carver and was using him for years before these special pieces.
I reckon they are just charging that price because they can, there are people who want something personally from Mamady, and are happy to pay an exaggerated price. What would be the point of a signed djembe if the price didn't go up.
It is hard to see why djembes are so dear any ways considering the real price of wood and carvers in West Africa.
People seem to accept a special piece should be 800 dollars but are then shocked at 1500?
I think both prices are over the top for a good djembe which is esentially, specially selected wood and well carved bowl.