In the midwest I see them for under $20 at about 5". A 2 footer you might get cheap or free from someone that can't house it. Around here they get released in lakes, and are a nice surprise for fishermen.
I bought one for my brothers 3500 gallon pond. Paid $5 for a little 3" guy. 1 year later he's pushing 15-16". In an aquarium with warm water, heavy feeding, I'd bet you could get it even bigger than my brothers in that period of time.
When they are small, they go for roughly 1 dollar to an inch.
Whatever anyone would pay. If you are lucky, you may find someone who will pay you a small amount but chances are you will struggle to unload it for free and to an appropriately large home. I've heard people sometimes try to get them for free/little money for eating... albeit it is risky for their health.