You didn't include the cost of the base OS. There's plenty of factors you also left out for new consumers, such as you said the case, hdd, keyboard and mouse. It's not a genuine comparison until you include the cost of all base software and hardware to make the experience.
You re-use your existing os key, you are allowed to do that (you can call and they will activate it if needbe, I've done that) and the assumption is that you have an existing pc to upgrade which just about everyone does. If not then you can still buy a case, hdd, keyboard and mouse for <$100, or buy a complete pc for $300 or so online, like I said in the other thread they are on sale every single day here, then add either a 670 video card and be done with it. It really isn't anywhere near as complicated as people make it out to be nowadays. Then people won't have to cry on forums for years about poor texture filtering, crappy frame rates, etc and instead just play games.
That's all Joe Gamer wants.
Which Joe Gamer? The Joe Gamers I know who have kids also want to watch home videos, movies, and stuff like that, things which aren't as good on console. They also want to browse the web, something which consoles to date have been terrible at. So you'll have to clarify which Joe Gamer you are talking about, because the ones I know seem to have different needs than you. In any case it looks like you are screwed in the UK, I asked some UK friends and your pc pricing there is terrible, almost double what it costs here. That explains why they buy parts here when they are here and bring them back there. So in your case just stick with console.
I dont think everyone is willing to waste hours trying to check hardwate compatibility, find the best prices for the best hardware money can buy and then when he purchases all the parts (maybe from the internet from various sellers) put time to build it themselves. The console is ready to buy and plug in. Few are experts and patient enough to build their own PCs
For the record my gaming pc has been more solid than my 360, I've had no problems at all with it this year. It just runs and runs, I haven't even had one game crash. I haven't had to do any troubleshooting at all either, it just all works. I've been on Windows 8 now so as a bonus the machine cold boots in about 13 seconds, but I just sleep it anyways. Aside from saving a ton of money on games, a great bonus especially on Windows 8 is all the games I get on Win8 store work on every pc in the house. I have them in the office, living room, my laptop and soon my tablet. Just right click and "install all", bam done. Same with my steam games, I have them everywhere I want. It's all just so cheap and so damn convenient that going back to console seems like an extremely tough sell, but to each their own.