The only way it gets less costly to stay is by lowering the cost of living for American workers. Many of these companies already pay a negative corporate income tax, often negotiated with specific loopholes. Boeing, off the top of my head, and Wal-Mart, but both continue to import foreign goods, fire experienced labor for new-hires, and outsource or export manufacture.
https://www.theatlantic.com/business/archive/2017/11/trump-corporate-tax-reform-jobs/544487/
We've been cutting corporate taxes since the 80s and individual taxes on the top earners since the 70s, but companies keep offshoring faster and faster. If taxes are the problem, why hasn't cutting taxes worked? Because I know you don't think the solution is lowering the standard of living for workers, you've said as much.