Ok, now that the range is live I can see I was partially wrong about the prices. The one in the publicity shot was over £1000 though. There are 14 models in the range, 7 of which are well under £1000 and another which is barely under at £995.95. If you want it delivered then add another £14.99 on to it. You also need to buy keyboard, mouse, speakers/headphones and a monitor unless playing on a tv which makes most of the others close to or over £1000.
I wouldn't want to play games on a £300 system. You would have to make far too many compromises if buying new and are limited to low end gaming which you may as well go and buy a console. You could do better for the £300 by going second hand and self building but that's not who these systems are aimed at.
You are right, pc components do not magically age quicker. Games advance though and demand more from a system unlike console games that are designed to work on consoles with a specific list of components. I certainly wouldn't like to play Fallout 4 or many other modern games on a 5 year old pc. No doubt it can be playable if settings and resolution are turned down but that defeats the object of going down the pc route and you may as well buy a console. If you want to play a modern game at a decent resolution with all or most of the settings turned up and play it as it was designed to look then you need to upgrade at least the gpu.