I want to demystify how compound interest actually works with real 40-year numbers, because the standard explanations always feel abstract.

If you invest $5,000/year ($417/month) starting at age 25 and stop at 35 — just 10 years of contributions, then let it sit — at 7% average annual return, you'll have approximately $602,000 at age 65. Total out-of-pocket: $50,000.

If instead you wait until 35 and invest $5,000/year all the way to 65 — 30 years of contributions — at the same 7% return, you'll have approximately $472,000. Total out-of-pocket: $150,000.

The person who started earlier, contributed for one-third as long, and put in one-third as much money ends up with $130,000 MORE. That is the compounding effect in one example.

This is why 'start as early as possible' is not a platitude but an actual mathematical advantage that cannot be recovered once the time is gone.