The sad thing is, they're not. A lot of people have not been paying attention to PC costs. This is what they cost now. I've seen a few "make your own" builds online. If you use new parts, you might save 80$, and you generally don't get the form factor, efficiency, integrated Steam Controller puck, or visual appearance with those builds, plus, you know, you're building then yourself which should be counted for at least some cost in most cases. Anything that saves more than that involves used parts or parts the person making the video/article already had, which is fine if you have them but not generally comparable.
You can get a better deal on some consoles at the moment, but I wouldn't count on that to last. The Switch 2 has a price increase scheduled. The Xbox line has a price increase scheduled. PlayStation did one earlier this year. Rather than being a permanent situation this feels like everything going up, just irregularly rather than smoothly, so sometimes one thing feels like a better deal, sometimes another, but it's not obvious that any of them are much better on a longer time frame. If you're looking out at the console versus Steam Machine and thinking the consoles look better for your use case, you don't already have one, and you're interested in one of them, I suggest moving sooner rather than later.
The Steam Machine is what got noticed, and earthed a lot of anger about prices, but it's not particularly out of line or especially expensive. The whole market is screwed up.