Worth, ∨ At , [so many] years' purchase Meaning, Definition & Usage

Definitions
  1. a phrase by which the value or cost of a thing is expressed in the length of time required for the income to amount to the purchasing price; as, he bought the estate at a twenty years' purchase. To say one's life is not worth a day's purchase in the same as saying one will not live a day, or is in imminent peril.

Webster 1913