Are lottery tickets ever a wise investment provided the jackpot is large enough?
I think playing certain kinds of lottery is as economically sound as buying certain kinds of insurance.  A lottery is an inverted insurance. Let me elaborate.  We buy insurance for at least two reasons. The first one is clear: We pay a fee to protect ourselves from a risk which we don't want to (or cannot) bear. Although on average buying insurance is a loss, because we pay all the insurance's office buildings and employee's salaries, it still is a reasonable thing to do. (But it should also be clear that it is unreasonable to buy insurance for risks one could easily bear oneself.) The second reason to buy insurance is that it puts us at ease. We don't have to be afraid of theft or of a mistake we make which would make us liable or of water damage to our house. In that sense we buy freedom of sorrow for a fee, even if the damage wouldn't in fact ruin us. That's totally legitimate. Now I want to make the argument that buying a lottery ticket follows the same logic and is therefore not economically unreasonable at all. While buying a lottery ticket is on average a loss, it provides us with a chance to obtain an amount of money we would normally never get. (Eric Lippert made this argument already.) The lottery fee buys us a small chance of something very valuable, much as the insurance frees us from a small risk of something very bad. If we don't buy the ticket, we may have 0% chance of becoming (extremely) rich. If we buy one, we clearly have a chance > 0%, which can be considered an improvement. (Imagine you'd have a 0.0000001% chance to save the life of a loved one with a ticket who'd be 100% doomed otherwise. You'd bite.) Even the second argument, that an insurance puts us at ease, can be mirrored for lotteries. The chance to win something may provide entertainment in our otherwise dull everyday life. Considering that playing the lottery only makes sense for the chance to obtain more money than otherwise possible, one should avoid lotteries which have lots of smaller prizes because we are not really interested in those. (It would be more economical to save the money for smaller amounts.) We ideally only want lotteries which lean on the big money prizes.