Maybe, but I use my PS3 as much as I use my laptop. Between games, movies, streaming movies and musics, my PS3 is nearly always doing something if I'm home. A new tower might replace some of that, maybe. But with my PS3 running through my big screen and my surround sound, all of that will look and sound better out of my console. Unless I spend even more money for that.
Admittedly, I haven't been into PC gaming for about 4 years now, but I was always replacing something every few months. I easily spent as much a year on my gaming pc as I did on my PS3, and I bought the big one at launch. And constantly fixing my mother's PC, I can tell you it's still expensive. In the last 2 years, I've spent enough on her systems (buying most everything from Newegg) to buy 3 PS3s.
Then you have the upgrade pace. Sure, the PC hardware upgrades faster, but it also needs upgraded faster. The version of Windows I was running on my gaming tower when I bought my PS3 isn't even supported any more (XP). A couple months later, I got a new work laptop with Vista, which has already gone away. My current laptop is running Windows 7, which has also been replaced by Windows 8. That's 3 brand new versions of Windows that have come out since I bought my PS3, none of which are cheap.
Now, I've been piecing together a gaming pc for a while now, but I still need a copy of Windows if I'm going to be gaming with it. If I go with 8, I'll need a touchscreen to actually utilize what's good about it. Even going with 7, I'm going to be spending $100 (assuming I go with the cheapest one, I usually went with the Professional version for use with work). I know there's other hardware I know I'm going to need to get it online, but I'm going to have to work and tweak to figure out what I actually need, then get everything working together for optimal performance. And the chances are that I'm going to have to replace at least some of the parts, as they're all second hand from systems that were already damaged. I don't know if any of them are even any good.
With a console, I don't have to do that. I plug it in and go. Everything is optimized for me. I don't need to worry about drivers, or if my graphics card is good enough to run this new game I want, or diagnosing what's wrong with the system this time.
Available to play (on PS3): Burnout Paradise, Black Ops 2, Borderlands (1), DC Universe Online, Doctor Who: The Eternity Clock, LBP Karting, Midnight Club: L.A., Need For Speed: Hot Pursuit, Need For Speed: Most Wanted, Portal 2, Red Dead Redemption, Saints Row the Third, Split Second, Tom Clancy's Rainbow Six Vegas 2, Tom Clancy's Ghost Recon: Future Soldier