Not only do you have to build them, but in all those builds the cases are several times larger than the Steam Machine, so they are not actually equivalent. If you care about the form factor, there is nothing directly comparable.
These options are up to 10 times bigger than the SteamMachine, approach almost twice the power draw, and are up to 2.8 times louder than the SteamMachine. They aren't even close to comparable... so why exactly are they making this apples to oranges comparison? No one is assembling a PC to put under their TV, and even if they are, ignoring the obvious form factor, heat and loudness issues... they'll most likely still want to install SteamOS for a "console-like" experience, which is still a win for Valve...
First option:
* 35 litre case (~10 times bigger than the SteamMachine)
* ~250W power draw (vs. ~185W SteamMachine)
* 32-36 dBA (vs. ~23 dBA SteamMachine)
Second option:
* 35 litre case (~10 times bigger than the SteamMachine)
* ~285W power draw (vs. ~185W SteamMachine)
* 32-36 dBA (vs. ~23 dBA SteamMachine)
Third option:
* 19.2 litre case (~5.5 times bigger than the SteamMachine)
* ~295W power draw (vs. ~185W SteamMachine)
* 34-38 dBA (vs. ~23 dBA SteamMachine)
Fourth option:
* 19.2 litre case (~5.5 times bigger than the SteamMachine)
* ~275W power draw (vs. ~185W SteamMachine)
* 32-35 dBA (vs. ~23 dBA SteamMachine)
The power consumption is a little silly to compare unless you are operating solely off-grid. It would take a few years of gaming daily for a couple of hours a day to make up for the price difference (assuming $0.20/kWh).
Physical size is definitely a bigger concern, nothing can beat the Steam Machine. But I do prefer the long and thin design like the PlayStation series has always used. It's easier to fit that on the shelves inside a TV stand that were designed to hold cable boxes and DVD players or it can fit upright behind a TV. I'm not sure if I actually have room to put a Steam Machine behind my TV without it overhanging the edge a bit.
As for loudness, that's a bit more subjective. It depends on how far away you are from the PC and how loud you play sound or if you're using a headset. Just totally based on my experience, games that are very quiet are usually the low-resource indie games that wouldn't be pushing my GPU to max fan speed anyway. The games I have that really push my GPU tend to have pretty loud sound design.
It's not the price of power that matters, it's the heat produced. Every extra W consumed is an extra W of heat that needs to be handled, and for consoles that tend to be chucked into confined spaces, that's an issue.
Loudness might be subjective, but if we're trying to compare builds, they should at least be in the same ballpark.
Looking at this article, they seem to only care about one dimension of this product: cost. It would have been far more interesting if they explored: cost, performance, size, heat (by proxy of power consumption), and loudness.
This is the old “why buy a prebuilt PC when you can DIY for less”. Which is true, but completely misses the point that may people will happily pay to 1) not have to build it, and 2) have e2e warranty, and 3) have someone else do the software setup.
We can debate if it’s the most efficient use of money for a technical person, but it’s indisputable that many people get enough value to pay for the prebuilt.