How do steam machines compare to PCs for price vs performance? I’m trying to decide whether i should build my own desktop or get a steam machine and install linux on it.
Build your own, if you know what are you doing go for it. You get to chose your own spec and you can upgrade if need be. (I don’t really know if you can tweak steam machine). If you never built your own pc ask for help, online, someone you know… I think you will get a much cheaper pc but stronger than steam machine. 
Edit : You can upgrade a steam machine but it is hard… And they say it is “console like” sooo…Source
If you are capable of building your own desktop and such, you’re not really the steam machine’s target audience. You’d definitely be better off building yours.
Yeah if you have the time, funds, and knowledge, I would definitely say build it yourself.
I was just wondering if they were trying to subsidize or sell at a loss like consoles do.
http://store.steampowered.com/sale/steam_machines
Nvidia Geforce GTX graphics cards? Intel Core CPUs? How awfully specific of them. Is that a 200$ GTX 960 or a 650$ GTX 980? Well, considering the price of the entire thing (450$) I’d guess they’re intentionally vague since they’ll definitely use the cheapest hardware they can get away with. That being said, they’re still significantly more powerful than the “next gen” consoles.
[quote]The Alienware Steam Machine combines the awesome experience of console gaming with a massive library of over 1000 games, all in full 1080p HD on your TV. You’ll experience powerful and immersive gaming with the high performance NVIDIA® GeForce® GTX GPU 2GB GDDR5 graphics and Intel® Core processors.
[/quote]
The sad part is that it’s 2015 and this is actually impressive for console players…
To add to what everyone else has already said, this is a very helpful community: http://www.reddit.com/r/buildapc
Check it out if you do choose to pursue a self-built machine! (I highly recommend doing so) 
Some comparisons here:
http://www.tomshardware.com/s/steam+machine+comparison/
The site promotes building your own, so there will be bias.