You will never "make" that. Here's why:
Assume your gross earnings for 2018 are $300,000 and you are under 50 and contribute the maximum of $18.500 to your 401K.
300,000 - 18,500= 281,500
281,500 is your taxable amount
Federal Taxes (Married Filling Jointly) - 50,379
(This rate expires in 2024)
Social Security-7,960
(Cap amount at the present time)
Medicare Tax/Surtax- 5,355
(There is no Cap on Medicare)
State Income Tax- ?
You only "made" 236,306 less any State Income Tax
If you reach the 12 year pay by the amendable date and the next Contract takes 5 years to negotiate you must take inflation into account. Subtract about 9,000 for a 5 year window.
https://www.usinflationcalculator.com/
Math is hard, arithmetic doesn't have to be.
After my nap and cookies and milk I'll be doing the arithmetic that demonstrates how much a 10% non-taxable employer match is worth.