It refers to a person who will go to great pains to save a few Pennies here and there, but think nothing of spending a large sum of money on something they do not need. 'Penny-wise and pound foolish'...
What Benjamin Franklin ment was any penny you don't waste is the same as earning a penny. Pennies don't mean much anymore, so think of it as $10. Basically, not wasting $10 is the same as earning $10.
Nowadays there are 4100 pennies (pence) in £41 because there are 100 pence in each £1Before money was decimalized in 1971 there were 240 pennies in £1.A modern penny is worth 2.4 of the old pence.