Michigan couple spotted a lucrative lottery loophole

Summary of the loophole from the article (within the first three paragraphs).

once the Winfall jackpot reached $5 million – and no one had matched all six numbers to win – a "rolldown" would happen. That meant the money rolled down and was split between winners who matched just five, four or three numbers.

Jerry quickly calculated that if he spent $1,100 on 1,100 tickets, odds are he'd have one four-number winner that would pay out $1,000, and at least 18 or 19 three-number winners that paid $900. That meant his $1,100 investment would yield a $1,900 return, for a tidy profit of $800.

> After nine years, the Selbees had grossed over $27 million in winning tickets – for a net profit of $7.75 million before taxes. That's when a Boston newspaper started investigating locations where lottery tickets were being sold at an extraordinary volume. That triggered an investigation by the Inspector General.

9 years of repeated lottery winnings by a single family and somehow nobody at the lottery noticed. Amazing.

A similar case is also described in Humble Pi: When Math Goes Wrong in the Real World by Matt Parker, which I'd recommend.

However, in that case it was profitable to buy _all_ lottery numbers. Which is a massive logistic operation.