[mattficke]

They’re progressive jackpots, the prize pool increases until someone wins, at which point it resets. So a ticket for an individual drawing can be +EV if no one has won in a while, with the excess money coming from players in previous games rather than the lottery administrator.

[d1sxeyes]

That would be true if each combination could only be bought once.

However, as you cannot know in advance how many other players will play, or what numbers they will select, you cannot properly calculate an EV. Further, lottery players rarely play randomly. A winning combination made up exclusively of numbers less than 31 has a higher chance that someone else will have the same numbers (as many people use birthdays to pick the numbers they will play).