If I make $150,000 a year for 15 years, how much money would I have?
Think of it this way. Look at America. Land of the credit card and debit card. Calculate the post tax income. Something like 50% of those will spend from just a bit more than that amount to a whole lot more than that amount.
We aren't taught to live within our means. You may get a raise next year and theoretically make up the difference. We aren't taught (any longer) to save. Credit card companies want you to max out, pay the minimum, and pour money on them.
Dave Ramsey will try to teach you a different approach. He's pretty good.
A serious answer to your question. You would likely live and spend differently than if you made 1/2 as much. You also pay tax. If you can save 10% of your earnings that's pretty fair. If you can save more, you're on your way to becoming wealthy. So 15 years,$150k present income? Likely savings if it was a goal for you? $200k - $300k. If you lived in a tiny house on ramen noodles with no car etc, maybe $1mm.