I'd be willing to "do nothing [for pay]" for as little as $25k per year in 2015 dollars, and probably even for slightly less than that. You could raise the alternative payoff to $5 million and I wouldn't change my mind. (I'm assuming that taking the job for several years and then living off of savings defeats the point of the hypothetical.)
The freedom to do whatever I want with my time - art, volunteering, personal projects, travel, learning, meditation, etc. - rather than committing most of my natural life to drudgery would be worth quite a lot to me. Not knowing what you'd do without someone telling you what to do every day is the mark of a dullard.
My threshold might be something more like $35K, given NYC cost of living and my stupidly expensive student loans, but besides that
exactly this. "Doing nothing at work" is most emphatically
not the same as "doing nothing" in total.
To say nothing of the fact that I wouldn't even know what to do with $200K a year, let alone $500K.