"Extraordinary gains?"

Ordinary gains are about 4% a year (long-term returns of broad investments in the stock market, adjusted for inflation). If you buy a piece of equipment for $100 it should return $4/year (on top of maintenance costs, depreciation, and the like) otherwise you'll do better by buying a stock-market index fund.

How much do you think it would cost an arbitrary manufacturing company to switch over all their tools and equipment to metric measures, update and test all their designs and schematics, run them through any applicable regulatory agencies, and such? Include the cognitive up-front cost of switching, maintaining dual toolchains and inventories for any gradual transition, the opportunity cost of the profitable projects you would have to postpone while your company experts see to the metric switchover, and everything else. Consider adjusting the return downward a little to account for appropriate risks in this process.

Do you see savings substantially in excess of 4% a year? If so, that's extraordinary, and a worthwhile investment! If not, the company would do better for itself and its shareholders by spending money elsewhere, or returning that money through dividends or stock buybacks so it can be put in a stock market index fund.

Clearly I was talking about switching the entire American society from imperial to metric. Your switch of focus to the impact on a single company and it's return on capital is certainly interesting but I am not 100% convinced it's germane. It's not necessarily a good idea to apply a Wall Street lens (quarters trump decades!) to every decision. Other countries around the world have successfully absorbed the short term pain involved and are reaping long term gains. Sticking to imperial forever means paying an imperial deadweight tax forever.

Other countries around the world have wasted billions and trillions on a lot of things (senseless wars, for starters) and gotten through the short-term pain that this has caused - that doesn't mean it was a good idea.

If nothing else, the $N billion of nationwide switching costs could have been used on, like, renewable power, or something.

It sounds as if you really think it's a good idea to stick with imperial. In your opinion is this a common attitude within the technologically sophisticated section of US society? I didn't think it was but maybe I am mistaken.

I prefer metric, from a policy perspective, I just think the path dependence has too strong a case to revamp industrial toolchains. (Changing the road signs and temperatures, by contrast, is both trivial and useless.)

Other things which are better that we'll probably never have include broader gauge railways, Dvorak for everyone, Wankel engines, and Betamax (vs VHS).