The union labor cost per car made in the USA is 8%. I doubt if anything manufactured in the USA is going to need more labor than a car assembly line.
You picked a bad example. Auto manufacturing is one of the strongest manufacturing subsectors in the U.S. today. One big reason for it is that UAW workers are in decline, and most of the growth in the industry is in non-union plants in the South.
Talk about economic illiteracy! The average car costs ~$25,000. That means that $2000 dollars of that cost is union labor. What makes you think the cost will stay the same percentage for a different product? What if the dollar cost stays the same per worker? How many 10 cent widgets will make up for $2000 labor?
Anyone who thinks cost scale linearly for all products has never run a business in their life. I'm not against some tariffs, but I am against stupid reasons... and yours is as stupid as they come...