I agree that it is all about cost, however this is far more "local" to many US citizens than they might imagine. For example, most of the coke bottles outside of the US come in half litres, while in the US they come in 20 fluid ounces (this is certainly true for many other products, too.) Hence, companies that make coke filling machines must accommodate the imperial system on top of the metric system, as well. Given that the metric system company can easily grab most of the market share, it should eventually be able to get larger economies of scale. In the end, it could very well be that machinery to supply imperial unit sized products becomes more expensive, a cost that will most certainly be relegated to the consumer.