1 million dollars in net worth is achievable with investments early in life in a 401(k) or other tax deferred retirement fund. ~$300/month starting at age 20 gets you to $1,000,000 which is about 10% of the income of someone making $40k/year. That’s not completely out of reach.
It would take you a lifetime of saving 100% of that ($1,000,000 initial investment + $40k/year), a 10% interest rate (which is ridiculous), and daily compounding to reach $1bil. That is the difference between $1mil and $1bil.