You’re buying the right to actually dream until Friday night (till Motzoei Shabbos until you can find a way to check the numbers b’hetter).
Insurance policies work by one taking a small hefsed now (premiums) to prevent a big hefsed later. Lottery is taking a small hefsed now for a potential revach later. One is attempting to remain a muchzak in what you have. The other is an attempt at an increase.
Also the risk in insurance policies is based on actuarial tables to be realistic. One calculates what the aggregate risk in all of his potential customers and sets the rate at what is theortically a couple of points more than what he expects to pay out. Risks are calculated by the customers in a similar way (albeit without consulting actuaries) and they elect to buy the policies, or not. The odds of winning the lottery are off of any actuarial table. No one invests based on any EV having any realistic values. Your purchasing a dream, that’s it.