I just got a male Ivory from the Daytona show for $325 (got it pretty cheap) and saw a larger one (guessing around 600-700 grams) for $400. Also just saw some male ivorys for $375 to $450 at the tampa reptile show today.
Another thing I just thought of, is that to ask about the temperament of the snake, you probably don't want an aggressive one. I have a few balls, and most are plenty friendly, but a couple will strike if you just reach in, not being able to see to read their body language could get you bit. Not trying to discourage you, just be careful.