They didn't cheap out on lights. They didn't want to add a light to the cockpit because changing anything meant pilots would have to be trained on it. Airlines,

They didn't cheap out on lights. They didn't want to add a light to the cockpit because changing anything meant pilots would have to be trained on it. Airlines, specifically American, didn't want to incur the cost of training of a new plane that could compete with Airbus. So to get the sales Boeing promised a million dollar kickback per 737 MAX sold if American 737 pilots had to get training to fly it. The cockpit had to remain the same in every way to avoid it.