It's kind of the opposite of sour grapes, it's like signing the purchase of a car but then you find out somebody else is selling a similar car for 20% off and y

It's kind of the opposite of sour grapes, it's like signing the purchase of a car but then you find out somebody else is selling a similar car for 20% off and you feel like you don't want to buy the car anymore but you signed but then the other guy can't sell you for some reason and you're all too happy to let that slide.