The Meaning of Life, the Universe, and Everything.
Well, I would give you exactly $0.00 for your minecraft diamonds, so about that much. They're a virtual commodity with no use or value in the real world. Their occurrence within the Minecraft world is unlike that in the real world. The only correlation is that diamonds are a relatively rare commodity in both worlds. Besides, while they are relatively rare in Minecraft terms, your 9 chests filled with diamond blocks represents a supply greater than any practical need beyond excessive luxury, so you have effectively flooded the market and greatly reduced their value.
I mean if i was playing on a server with my friends and if diamond was so valuable i would sell 1 stack for a dollar other than that it wouldn't sell for nothing but it would make good lunch money if we were competitive.