There's a lot of talk about work-life balance on HN, and I usually lean way towards the "life" end of the spectrum. For the last few years I've only been doing a couple of hours of paid work per day. But yeah, I'd be happy to work 70 hour weeks for $3M per year.
I think I might compromise to work 70 hour weeks for $3m for one year. The trick is, you don't get to pick when that year happens, and there's actually a lot of build up to get to where you're worth $3m a year. There's a couple of Paul Graham essays with this as one of their themes:
http://paulgraham.com/wealth.html
http://paulgraham.com/start.html
I love the idea, but I don't think I'm good enough to pull it off, and I don't like the odds.