Since you've gotten this far in the thread I know you will find the book I am recommending fascinating.
It was written in early 2006 before the crash but holds true today. The author was a successful exec in Manhattan and then took a high C level position in rural Wisconsin at which time a mega corp bought them out and he became a multi-millionaire over night, so he quit, having made his "number".
So he decides he wants to write a book about The Number because he had been slaving for it all his life and suddenly he gets it. He interviews folks from all stratas of society and age groups and (spoiler alert) realizes there's no such thing as a "number" but rather a choice of what lifestyle one wants when one is finished with w**k. Basically the premise is one will never reach a solid numerical number because we all think we won't have quite enough with the spectre of taxes, healthcare and inflation rising, disaster around the bend, boomerang kids, etc. And the wealthy will never feel that they have enough.
Lee Eisenberg, The Number
Lee Eisenberg - The Number - A Completely Different Way to Think About the Rest of Your Life
The Number: What Do You Need for the Rest of Your Life and What Will It Cost?: Lee Eisenberg: Amazon.com: Books
He did come up on page 234 with a summary because he felt he would come under criticism if he didn't have
Some Number in a book by that title, so he averaged out what everyone told him:
COMFORTABLE: Lives in one place, eats/travels modestly, though better than most, then you annually need $50-$100K, which means your Number is $1-2 mil.
COMFORTABLE+: likes occasional upgrade, mid-priced country club, maybe small second home, then you annually need $175-250K, which means your Number is $2-5 mil.
KIND OF RICH: likes finer things, eats/drinks/travels well, gives $ away, picks up checks, couple of nice houses, then you annually need $350-500K, which means your Number is $7-10 mil.
RICH: spends weeks/months abroad, exclusive gated golf communities, place for every season, fractional jets, sits on boards, then you annually need $1 mil, which means your Number is around $20 mil.
He obviously also interviewed a lot of rich people...One take away was that most people don't even start thinking about it until it's too late and another point is that unless you've hit a home run career wise and are great savers you probably will have to reduce you're life style in retirement. He eviscerates the financial services industry (although is kind to Vanguard) and warns against brokers and financial planners.