Without the essentially free oil, the flow of food into Iraq would be a trickle. Some food gets dropped off in the north, and the rest is carried into Iraq proper. That oil trade violates the UN embargo, but sensibly no one complains, because the population would otherwise starve. The Kurdistan Front generates income by taxing the trucks on their way to Mosul, although revenues fall far short of what is needed. Many obstacles to normal economic activity exist in Iraqi Kurdistan.
People carry huge wads of bills.
Nevertheless, the supply and distribution system has not broken down, as it did in the former Soviet Union. The Middle East has a long commercial tradition. The embargoes also interfere with private-sector activity. Kurdish peasants could not obtain seed, fertilizer, or pesticides for the last harvest. As a result, the crop was about half what it might have been.