When a person is convinced on something unknowingly by being presented three options. Option 1 is more than necessary. Option 2 is just right. Option 3 is inadequate and makes option 2 look more desirable. Slight variation from the children's story. Option 2 is always chosen.
Salesman: This one is expensive/big/overkill. This one is mid-range/practical/affordable. This one is economic/cheap/low quality.
Consumer: Ah I think I'll go with option 2. You tricky salesman!
Salesman(To Coworkers): That's how the goldilocks approach is done my friends.