Adam Clarke on Genesis 47:14

Gathered up all the money - i. e., by selling corn out of the public stores to the people; and this he did till the money failed, Gen 47:15, till all the money was exchanged for corn, and brought into Pharaoh's treasury. Be sides the fifth part of the produce of the seven plentiful years, Joseph had bought additional corn with Pharaoh's money to lay up against the famine that was to prevail in the seven years of dearth; and it is very likely that this was sold out at the price for which it was bought, and the fifth part, which belonged to Pharaoh, sold out at the same price. And as money at that time could not be plentiful, the cash of the whole nation was thus exhausted as far as that had circulated among the common people.