PC fanatics people (and mostly Apple hater) would argue:
With $2000 you can build a $1600 gaming CPU (i7, XFire 6970 and all other components) + $400 cheapo ugly TN panel display. They will argue not everyone needed an expensive display. Answer this then, why bother using expensive and multiple GPUs but you use a crappy display?
It's a bit unfair to be honest. When you have to include 27" IPS 1440p display .. well those people are just ashamed and dead silent. They end up spending $2500-ish with their computer. Cost more!! The next thing is that they just can say "But ... but .. but" and ranting.
Whenever you try to match custom built PC into $2000 while keeping that gorgeous 27" display, well you just can't beat iMac. You'll just end up having the same spec with hi-end iMac with some bonus (i.e upgradeability system and also power hog computer).
I challenge OP to build custom PC that can surpass equivalent iMac, cost $2000-ish and still using 27" IPS WQHD display. Can you do that?
I hardly upgrade my computer anyway. If I want something new, I'd just sell my whole computer.
The cost of partial upgrade is not feasible anymore to me. For example: old model RAM cost more than new one, so if I have to upgrade old RAM slot on my main board, it would be more expensive than it should be.
Or having an old motherboard with LGA775 can only maxed out to Core 2 duo. If I want Core-i5 or i7 .. I need new motherboard, which not really cheap. So I don't really bother with upgrading my CPU anymore. Just waste of money and time to me.
Actually, that is incorrect, you can get a bit better hardware for the same price, assuming you build your own computer and purchase the Dell screen with the same specs as the iMac's.