The hours logged in his graph (per my understanding) do not show the work spent on searching and applying for jobs. And also tweaking your CV. There is a lot of overhead in doing this.

And then you have to log hours for: accounting, banking, and government papers. And then deduct banking and accountants fees. And then deduct your hardware fees (since you are paying for them yourself). No need for an office since you are can do it from home.

So is this really profitable or sustainable on the long term?

I live in a poor third-world country and I consider my break-up rate to be around $60/hour. There can be only one of these scenarios if you work for a lesser rate:

1. You cut on some expenses like an accountant/medication that might result in a disaster later.

2. You over-work yourself and you work on week-ends/no vacation.

3. You live with your parents, so you don't pay (or share) the bills.