If you work through the maths then the man's claim makes sense. If someone invests a million dollars in the stock market for the next forty years, and a reasonable assumption is that it doubles every decade, then they'll have $16 million in 2064 or 2065. The problem is that if inflation runs at around 3% during that time, the real value would be about $5 million in present day terms. A lot of the "if you invest $1000 per month into the market" calculations ignore this.