Or HaChaim on Genesis 47:15/אור החיים על בראשית מ״ז:ט״ו

1 ולמה נמות….כי אפס כסף, "why should we die …for there is no more money?" The people complained that Joseph had proved unwilling to accept any payment other than money in return for grain. They argued that they were not destitute, they could pay him with other chattels; why should they die merely because they could not pay cash? This is why Joseph replied that he was willing to accept their cattle in payment only "if indeed there is no more money." Joseph's reason for all this was to impoverish the Egyptians so that his brothers would not be in an economically inferior position vis-a-vis the Egyptians. Joseph was very clever not to accept any payment other than money as long as there was cash around. As long as the Egyptians still had their livestock they would have to provide fodder for their animals; presumably one effect of the famine was the absence of grazing land. The Egyptians therefore had to feed their livestock with barley. This in turn led to the money supply becoming completely exhausted within a year. As a result of Joseph's strategy the brothers who arrived during the second year of the famine were wealthy compared to the average Egyptian at that time.

2The Egyptians may also have meant to convey to Joseph that they did have money but that they had no cash flow at that time. They were unable to collect their receivables. This was not something unusual as many people invested their money in enterprises in foreign countries, sending money on ships which were meant to import goods. Their argument therefore was: "why should we die since we have the necessary liquid assets and are only unable temporarily to collect that money?" Accordingly, Joseph told them that if they really did have money in the form of receivables he was willing to accept their livestock as payment for food in the meantime. The livestock served as collateral for the cash the Egyptians would owe him. As soon as they would collect their receivables he expected them to turn over the money to him.