$375 * 40 hours * 4 weeks * 11 months = $660,000 per "year"
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.
If you have year-round, full-time contract work with no downtime due to acquiring new clients or negotiating new jobs with existing ones, then you probably don't have enough clients to be truly independent.
I'm sure there are unforeseen expenses in all of those scenarios that would require some padding to insure against, but the contracting scenario is the one I'm most experienced with, and the assumptions behind your numbers have bitten me in the past.
subscriptions > one time sales
When cancellations equal signups (in this case 10 per day) you will stop growing. With the 10 signups per day as a base and a retention of 6 months on average that would mean that you stop growing after about a year and you'll end up with 1800 active accounts at that point for $36K per month in income.