You can't expect a person to see eye to eye with you when you are on him.
"See eye to eye" means to agree. A person will not agree with you if you treat them with contempt, so the phrase must express looking at someone as inferior. "Looking down on him" means to regard someone as beneath you, which fits and echoes the eye idiom.
looking ... down is the best fit.
If the price of a commodity increases by 25%, by what percentage should the consumption be reduced to keep the expenditure the same?