How much was that?
I got it for a five finger discount.

I've been jabbed

Whenever I walk past the candy rack, I give myself a five-finger discount.

"Dude! I got a five finger discount on those womens underwear!"

"How do you plan to afford that?!"
"Dude, calm down, I have a five finger discount."

The punishment for thievery in certain middle eastern countries possibly includes cutting off all five fingers from the hand that stole the goods. Hence, your discounted price of $0 includes five of your fingers, or a "five finger discount".

got myself a five finger discount on a pair of Levi's.