For years, it was an underappreciated wrinkle in the historic deal that merged the established National Basketball Association and the upstart American Basketball Association in 1976. The owners of the Spirits of St. Louis agreed to be paid a small fraction of the N.B.A.’s television money to comfort them for being cut out of joining the older league.

Their piece amounted to a sliver of the modest amount that CBS was paying the N.B.A. in those days. But if the share was small then, one particular term of the arrangement was attractive: the owners, Ozzie and Daniel Silna, would be paid the money every year in perpetuity, or as long as the N.B.A. existed ...

In 1980-81, the first year the Silnas were eligible to get their share of TV money, they received $521,749, according to court documents filed by the N.B.A. For the 2010-11 season, they received $17,450,000. The N.B.A.’s latest TV deal, with ESPN and TNT, is worth $7.4 billion over eight years. Soon, the Silnas’ total take will hit $300 million ...