bandit

Rur. to make a large profit. Joe's making out like a bandit, selling expensive cameras. Mary made out like a bandit, playing twenty-one in Las Vegas.

Succeed extremely well, as in He invested in real estate and made out like a bandit. This expression likens other forms of success to that of a triumphant robber. It may, however, come from an intermediate source, that is, the use of bandit (or one-armed bandit) for a slot machine, which is far more profitable for the house than for gamblers. [Slang; c. 1970]

A slot machine, as in It's amazing how many people think they can make money playing a one-armed bandit. This term refers to both appearance and function: the operating lever looks like an arm, and the machine in effect robs players, since it "wins" and keeps the player's money in an overwhelming majority of instances. [c. 1930]

To be highly successful in a given enterprise.