For example TV's. I would guess there is ONE labor hour in a typical TV imported form China(or elsewhere). I make this guess based on the rule of thumb that it takes 30 man-hours to make a car. This is documented fact. So my assumption is that a TV needs 1/30 of the labor to make compared with a car. Not a bad assumption so we'll go with that.
So when you buy a $500 TV you will pay for 1 man-hour factory labor. So let's say the TV is made in China. Labor is $3.00/hr. If that TV was made in the USA the labor would be $30.00/hr. The TV would cost $530.00 with higher domestic labor costs. So to make up that difference in labor costs a 20% import duty would do that little trick just fine. You could make TV's in the USA again and still have money left over! Well until your competitions moves back to the USA.
Don't disagree with me you'll look like an idiot.
I have built consumer electronics for twenty years (mostly cell phones). I can tell you they do not know down to the second how long it takes but they know instead how long it should take and how long it did take.
Mixed in with all the calculations are many intangibles like the cost of poor quality and the total cost of production. That number is a basically a monthly P&L statement. Direct labor is actually a small fraction of the cost of assembly most of the costs are overhead costs. Much of the overhead is a fairly fixed cost. Another huge intangible is the shipping charges. Expediting finished goods to the distributor or end user can be expensive. I had a friend who made transmissions for GM. Sometimes they would have to rent a small fleet of helicopters to get them to GM on time.