Rob somebody blind
Definition 1 of 1
Pro Tip 1/3Unfair Gain
Emphasizes taking more than is fair, usually in a sneaky manner. 
That mechanic will rob you blind if you don't watch the bill.
Pro Tip 2/3Negative Emotion
Carries a strong negative emotional charge; suggests victimization. 
I feel robbed blind by those hidden fees!
Pro Tip 3/3Exaggeration Effect
Often used to exaggerate for effect, not always literally true. 
Every time I buy popcorn at the movies, they rob me blind!