If you go to a show looking for the best snake you can buy for the lowest price, you may be able to find it on the last afternoon of the show. Many breeders do not want to haul their "inventory" back to their property and some therefore sell their snakes at a reduced price.
Now, the better snakes (higher quality, etc.) at a reasonable price usually sell early in a show - sometimes before the doors even open to the public.
It really depends on what you are looking for . . . . Good luck!