The "expected value of a ticket" is the probability of being drawn multiplied by the earnings associated to being drawn. ($1 is the price of the ticket which of course can be different).
So in this case probability is 1/2000 and the earnings would be valued $1000 (value of the plasma TV). The expected value is 1/2000*1000=1000/2000=$0,5
This means you should not buy a $1 ticket to play except if this really brings you LOTS of amusement ;)