Let's imagine they do come back. Let's say you have a toaster factory in Vietnam, which allows the US company to produce low-cost toasters for about $100. The factory workers earn $1 per hour. Now, due to the tariffs, a toaster will cost $146. And you say, "Okay, they just need to move their factory to the US and then the problem will be solved - no more tariffs. " Fine. Do you really think a US worker will work for $1 per hour? Even if you automate 80% of the factory, you still won't offset the 46% tariff. You will never get a toaster priced at $100. More likely, it will be $300.