The "closed" part of the ecosystem is Windows RT, in the sense that apps for that platform must come from the Windows Store. Windows 8 runs Steam very well, and has no such restrictions. Steam's not available on the iPad either.
You do realize both Microsoft as well as Apple are trying to separate the consumer market from the high end, professional market. The cheapest Apple device that allows side-loading costs 999 euro's. The cheapest win8 device that allows side loading will be at least 800 euro's.
I understand why. The biggest problem of the convential desktop is the ugly compomize between freedom, power users and professionals on one end, and casual consumer usage at the other end.
But that does mean, many of Valves current customers, that buy midrange devices, will end up on RT or iOS.
And the crowd on this site, will likely find the devices aimed for them moving to a more expensive and exclusive niche.
I think you have drastically misrepresented the computing market. The cheapest device you can put Windows 8 on is a $200 (maybe 250 EUR) netbook. It will then run whatever you want - including Valve. There are zero restrictions there. Can you game on that $200 machine? Sure, just probably not the games you want to play. That's hardly Microsoft's fault though, it's a $200 computer.
Amazon sells a Mac Mini for 600EUR (at least Amazon.fr does). That's about what an unsubsidized iPhone costs, right?
So where is this doom-and-gloom everything-is-locked-down-except-the-ultra-expensive actually coming from?
I think you're focusing on the wrong thing and getting the wrong take away. It's not about the price. It's about the experience. It's classic Android vs iPhone (for some at least): do you want a phone that provides a really good experience, or one that provides a mediocre (well, now really good) experience but with many fewer limitations, more features and more options.
Do you want an iPad/iPhone/WinRT/Android tablet with "apps", or do you want an x86 device with the ability to run whatever binary code you want and an OS that enables that.
It's not about price, because you're right, I can find devices in both categories at literally all sorts of data points. But it is about the experience.
Valve's business RELIES on the experience that enables users to run, in this case, native code. Since they're being pushed out as a result of this shift... they're naturally trying to warn people and shift interest to a platform where they can more easily operate... or survive.
In fact, your example is ironic. People are more likely to go buy a $500 iPad than they are a $300 full featured Windows laptop. That's exactly what worries Valve. Or it should.
The cheapest Windows 8 device that allows you to install desktop software is exactly as expensive as you want it to be. It's a normal PC. Buy a laptop, buy a desktop, build your own; it doesn't matter. It's a PC. You can buy/build one and install Windows 8 on it. You won't see desktops at Best Buy running Windows RT.
The article speculates that the emergence of Windows Store app platform from the Windows desktop could become similar to the emergence of Windows from DOS, and that newer technologies will similarly only be available on the Windows Store app platform.
It describes the locked-down properties of the Windows Store, and, extrapolating from the current certification requirements for Windows Store apps, it asserts that a game like Skyrim would be denied certification on Windows Store in 2032 because of its PEGI rating.
