Part of Dave Ramsey's math on how you "could" get to $5M is basing that on taking $500/mo that would otherwise be a car payment, and putting it in a Roth IRA, from age 30 to 70, or something like that. Considering the principal would only be $240,000, I'm guessing he's counting on some optimistic rate of return, like a consistent 11-12%.
I really wish these so called financial advisors would get it out of their minds that $500/mo isn't a lot for a car payment these days. For comparison, I had a 2000 Intrepid. $22,389 out the door. I put $2K down, financed the rest at 0.9% for 60 months. Monthly payment was $347.66. And that car was nothing fancy. Sure, it was a major step up from your typical small or mid-sized car, although I'd imagine something like an Accord or Camry was close in base price, and could be optioned up even more.
But still, it was a Dodge! And by that time, about the cheapest wanna-be full-sized car left on the market (even if Chevy was trying to push the Impala as "full-sized" and by EPA standards, the Taurus/Sable barely made the threshold to full-sized status)
Anyway, adjusting for inflation, that $347.66 would be around $640 today. So $500 won't get you much. Plus, consider how high interest rates are these days, and it will get you even less.