But if you're a software developer like OP, then you need a computer. You probably want a second (or third) monitor. The computer probably needs to be replaced every few years, and you're probably getting a relatively expensive machine.
Add to that an office - desk, good chair, etc. If you're trying to save money, yeah, you might not be getting a fancy expensive chair. But if you have the money to spend, I'd argue it's still a good investment for your back. Etc.
Now you can consider all of these as investments, but then how much you make as a contractor has to take that into account.
(Btw, didn't get into this, but the article is missing a lot of things you need to think about as a contractor, e.g. there's often downtime between projects, sick days, insurance is usually a good idea, etc. I've been doing this kind of thing for basically 10 years, it's not as simple as OP makes it sound.)
Yes, they are.
> They are investments that can be amortized over many years.
So, they are capex rather than opex costs.
> I would argue time is infinitely more precious than money,
Were that true, the market clearing price of people's time denominated in money would be infinite. Which would be inconvenient, since largely money exists to enable the indirect exchange of time for time (largely, as labor).
This difference has existed for a long time. It's discussed at length in Max Weber's Protestant Ethic and the Spirit of Capitalism for example, which has funny things to say about the philosophy developed in Ben Franklin's autobiography.
If one has money then spending it is good, of course. The question is, what are we willing to give up to get more money, and for what. I would argue time is infinitely more precious than money, above a threshold -- but the threshold is very low.