That is absolutely true, although "reasonably" in this case works for average American household income (about 50k) if you don't live in a very high cost of living area. The same techniques that let a middle to high income household (50k+) retire early only let a 30k household make ends meet and save some money to retire comfortably around the "official" age of 65, but that's still much better than most Americans do. His thoughts on hedonic adaptation are pretty much the same as we talk about here (having probably drawn from the same sources), and not falling prey to the tendency to spend money without getting much utility from it is more key to the whole early retirement thing than earning power. That is to say, not spending money is more important than earning money.
not spending money is more important than earning money
On reflection, I think this is an oversimplification. Which is more important depends on how easy they are. For most of us, reducing spending is easier than increasing income. But if you're poorly enough paid, reducing spending may be incredibly hard and at least in principle you can increase your income a lot (special case: by taking a job, if you're currently unemployed and the tax/benefit system isn't too badly screwed up where you are).
Quick summary: "Hidden rationalists" are what I call authors who espouse rationalist principles, and probably think of themselves as rational people, but don't always write on "traditional" Less Wrong-ish topics and probably haven't heard of Less Wrong.
I've noticed that a lot of my rationalist friends seem to read the same ten blogs, and while it's great to have a core set of favorite authors, it's also nice to stretch out a bit and see how everyday rationalists are doing cool stuff in their own fields of expertise. I've found many people who push my rationalist buttons in fields of interest to me (journalism, fitness, etc.), and I'm sure other LWers have their own people in their own fields.
So I'm setting up this post as a place to link to/summarize the work of your favorite hidden rationalists. Be liberal with your suggestions!
Another way to phrase this: Who are the people/sources who give you the same feelings you get when you read your favorite LW posts, but who many of us probably haven't heard of?
Here's my list, to kick things off: