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Jerry and Marge Selbee, who did the arithmetic
A retired couple in Michigan read the rules of a game properly and found it paid more than it cost.
~$26mGross winnings over nine years. Entirely legal.
Jerry Selbee, a retired convenience store owner with a maths degree, spent about three minutes reading the rules of a Michigan game called Winfall. It had a "roll down": when the jackpot passed $5 million without a winner, the money cascaded into the lower prize tiers instead.
He worked out that on a roll-down draw, the expected value of a $1 ticket rose above $1. Buy enough tickets and you were not gambling; you were buying a slightly underpriced asset at scale.
He and his wife Marge started buying tens of thousands of tickets per roll-down, printing them over days at cooperative shops. When Michigan closed the game they found the same structure in a Massachusetts game and drove there instead. A group of MIT students had independently found the same flaw and were doing the same thing.
None of it was illegal. A state audit found the lottery had lost nothing — the syndicates paid for their tickets like everyone else. The game was simply designed wrong, and the Selbees were the ones who read it.