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.