$500 is cheap if it reaches $700 by the end of the year, $500 is expensive if it drops below $400. It just depends on your own view on bitcoin prices. I personally think $500 is cheap, but it is because I bought some at $600. 
400 have been seen to be a very strong resistant point, so i doubt it will fall below that.
Well, we did see the $340 level on the last major spike down. So I would not say that sub-$400 is off the table. Seems some respected analysts here are calling for a revisit to the mid-300s.