[kirpekar]

OK

100k principal, add 1k every month for 30 years. Compound at 7% --> 2M

50k principal, add 1k every month for 30 years. Compound at 7% --> 1.6M

Withdrawing 50k today costs you 400k in retirement

400k = 20% of 2M = 8 years of your 40 year career

[ronaldx]

Yes, you've failed to consider the time value of money. https://en.wikipedia.org/wiki/Time_value_of_money

50k today is worth more than 50k in the future.

(Consistent compounding at 7% is extremely optimistic, even before considering inflation at 3%+).