Why can't companies make inch-pound products to sell here and make metric products to sell outside the U.S.?

This would raise our costs for buying inch-pound products and also make the metric version of the products priced considerably higher so foreign customers won't buy them. A manufacturer's expenses really increase when two production lines must be run (one for inch-pound and the other for metric products). Metric and inch tools, machinery, and parts must be kept separated, must be stored and inventoried, adding to the cost of their production. There are additional costs for record keeping, warehouse space, and other factors, such as mixing orders so non-metric products might accidentally be sent to metric countries. There also is a good chance of workers' accidentally mixing up metric and inch-pound parts so products must be scrapped. All this adds to the price of a product. It's cheaper to make only one size and sell it to everyone.  more