While you're correct that a good PC is more expensive than a console - sometimes substantially so - the 'constant upgrades' thing doesn't really apply. Yes, you'd need to do that if you wanted it to stay 'top of the line' forever, but that would be like buying a high end car and then trading it in for a slightly faster high end car a year later. Most of the time, you'll keep the same car for years and years.
I bought my gaming PC in 2012 (at about 3 times the cost of a PS4 - as I said the initial expense is a perfectly valid criticism!) and haven't upgraded it since. It'll still play pretty much every new game on 'High' graphics settings and outperforms the consoles. And as the games get tougher and tougher on the system I can just turn the settings down more and more instead of upgrading, and when I do upgrade in another few years it'll probably just be a graphics card, not a whole PC.
And of course - why would I need to upgrade? The majority of big games also come out on console, therefore they're somewhat limited by the consoles. I doubt very much something will come out on both console and PC that my PC won't be able to handle, so I should be good until the end of this console generation.