When the amount of money saved equals or exceeds the cost of an item or service, usually through an extended period of time.
This is very often used as a means of promoting a good or service, such as gutters,
food processors, juicers etc. As in:
"Now with Debby Meyer's
green bags, you never have to throw away your produce due to spoilage! Produce lasts up to 7 times longer, saving you
money and time. This product nearly pays for itself!"
Because Jack bought a home coffee
grinder, he can
grind his own beans at home! He no longer has to buy more expensive pre-ground coffee, so in
essence his new machine pay(s) for itself.