But the price doesn't have to fall $1000 in a day.  The price can half as often as it can double.  Here's a neat puzzle for you:

1.  You're given a sealed envelope, and are told (truthfully) that it contains $100.
2.  The man who gave you the envelope presents two other, identical looking envelopes.  He informs you that one of the envelopes contains exactly $50 (half of the money you hold), and the other $200 (double the money you hold).  
3  He offers you a chance to swap your envelope for one of the two presented envelopes.  
4.  Seems like it's in your best interest to swap, since if you choose badly (the $50 envelope), you only lose $50 (you had $100 before the swap).  If you choose well (the $200 envelope), you win $100.  Odds of you choosing the $200 envelope are 50/50, while you could win double of what you could lose.

See the problem?  Or did i misinterpret what you were trying to say?