Plinkertoo knows his stuff, I would tend to believe him. He's the resident guru on all things SUB.
Just because you got one for an excellent steal before doesn't mean that that wasn't the going price in his neck of the woods.
I do believe $500+ was the prevailing rate for the all metal Sub9, then when they reintroduced it as the Sub2000 in plastic you could find those for under $400.
Anyway, good luck finding a Sub9!