The expensive insulins are the fast acting insulins. Used in pumps and as a bolus dosage. This type of insulin is injected at the time it is needed. Basically at the time the user eats 15 grams of carbohydrates, they need one dosage of insulin. With a pump, the pump also releases a small amount of insulin throughout the day as the basal dose. Basically, this is the minimum amount of insulin the body needs to function. This description is overly simplified, but should be close enough to understand this principle.
A type one diabetic needs these fast acting insulins and a pump is a real godsend. But most type 2 diabetics can use N or R insulin. These are slower acting insulins and dirt cheap compared to the fast acting insulins. The reason a type II diabetic would use a faster acting insulin would be to take a bolus dosage with a meal. But, most type two diabetics can time their meals and control their CHO in such a way they do not need a bolus dosage. As the disease progresses they will eventually have the same needs for insulin that a type I diabetic does, but that is usually years after they are first diagnosed. For the most part, they can use the cheaper insulin; but, they have to time and watch their portions very closely when eating.
I said all that to make one simple point. The cost of the fast acting insulin is not due to type II diabetics who could simply make a change to their lifestyles. The demand is due to type I and long term diabetics and mainly those who use a pump. Those diabetics can both lower their insulin needs by lifestyle changes, but only by small amounts. Not enough to be the reason for the increased cost of these products.