I've noticed that sub adults are never on sale my assumption is that they're waiting to be sure of the sex of their tortoise or all their hatchlings get sold long before reaching that age.
honestly tortoise pricing make very little sense to me. one species the babies are more expensive than the adults and another species its the opposite. i guess wild caughts are driving the price down and hurting breeders.
The sub adults are in Craigslst. They are the ones purchased as babies and are now too much for the owner, who STILL has them jammed into a ten gallon aquarium. Just this year, I've found and purchased three such tortoises. All from Craigslist. (Though in much better condition.)