"Pound foolish" is not a necessary outcome of "penny wise", in this saying, but "the pounds will take care of themselves" is. Taking care of the pennies works w

"Pound foolish" is not a necessary outcome of "penny wise", in this saying, but "the pounds will take care of themselves" is. Taking care of the pennies works when one is, at worst, "pound neutral". But being "pound foolish" is an additional condition in the saying, which is not accounted for in the "take care of the pennies" saying.