Depends what you mean by rich, money rich, time rich? I'm not a millionaire but I only work 4 days a week 36 weeks of the year in a job I enjoy and I have no hassle from anyone. My wife and I have a good relationship where I do what I want, she does what she wants, and when the he/she wants are the same we do them together.
I've done the work your balls off for good loot and I thought it was a con TBH. You don't need a Porsche or three foreign holidays a year which is how they suck you in. The most important thing is time and health, and money can't buy that. I have a month in Oz every year, the odd weekend away with mrs thing, enough money to go flying and the rest is extra.
I have a couple of friends who you would consider wealthy. One is retired but goes nowhere without his laptop so that he can worry himself about his investments and the other doesn't spend any of the money he's salted away. The problem with being rich is that you can't go back to not being rich. If you've never had any money then you don't miss it, and more importantly you don't have to worry about it. (Providing of course that you have enough and you're not in debt.) Of course if I won the lottery I would be cock a hoop but then I don't need to be a millionaire, but I wouldn't turn the money down obviously.
To answer the OP if I could retire on an income of £5000 a month then I would consider myself pretty well off. I don't know what lump sum you would need to service that but I'm sure a million in the right places would probably do it.