You won't win if you don't try.
Worth it to me.
If I bet you $1 that the coin will come up heads against your $1 that the coin will come up tails, you have a 50% chance of winning $2, or a $1 return on average. So if you make that bet a million times, you should (statistically) walk away with the same $1 you bet in the first place. Whether or not you make this bet has no statistical impact on how much money you have, so do it if you want or not, doesn't matter.
Now, if I bet you $2 that the coin will come up heads against your $1, you have a 50% chance of winning $3 or $1.50 on average. Now you should make that bet as many times as you can. Make that bet a million times and you should walk away with $500k profit on average.
So in the first scenario, it doesn't matter whether you bet. In the second scenario, you're an idiot not to make the bet. Here's a third scenario:
If I bet you $1 that a coin will come up heads against your $2, you should never make that bet. You stand a 50% chance of winning $3, or $1.50 on average. So on average you lose 50 cents. Make this bet a million times and you'll lose $500k on average. Again, this is a bet you should never make.
So how about it. I'll bet you $1 against your $100 that a coin will come up heads. Want to make the bet?
You can't win if you don't try.
If you make that bet, your $100 ticket will be worth $50.5 dollars. Statistically, you're throwing away money. The same is true for the lottery, even at $640 million jackpot and only a $1 ticket. You're trading your $1 for something worth about 50 cents.
Justin
I wonder what the chances are that if nobody wins it could get to a billion?
If it hits a billion you should consider buying a ticket. Your $1 ticket may start to be worth a few cents more than $1. If the government were smart, they'd never let that happen.