The number for $520 an hour that was listed is actually very doable. My friend is a consultant at the moment and his price per hour is $500. Granted he doesn't get to take all of that home at the end of the day, the company he works for takes 25% of that, which still $375 an hour. Since he doesn't have to find his own clients (the company does that, hence the reason they take 25%) he has 40 hours of work a week. Since he is a consultant he can take anytime off he wants, but it is unpaid, lets assume that he works for 11 months out of the year, 40 hours a week.
That is still a substantial amount of money, yes it is not close to the illusive 900,000 the original thread was asking for, but it still shows a good example of what is currently doable if you have the skills.