You have that right. You need $1,000,000 in investments to generate $50,000 a year, assuming a measly 5% return. And with returns averaging 1% and inflation thrown in you are going to need a lot more than $1,000,000 to have a sustainable income through retirement.
I would be thrilled if my investments were returning 1%. All they are doing is dropping like a stone in value and my investments are fairly conservative.