Umm prove it. Build a PC that compares to a IMAC with the same SPECs. Sorry dude, you are wrong. Been in the PC field for over 20 years and as of today they are pretty equal with the same components with a much better warranty and look on the MAC side. Dell All in One, actually are more expensive in 27". Amazing.
Oh, and the IMAC comes with IPS display, with the smallest shell you will ever find, and 3TB Fusion Drive (SSD/HD combo). Wireless keyboard and mouse and a full 1 year warranty standard that covers both the software and hardware and as many calls as you want. That monitor itself is $1000 bucks plus from Apple or Dell any way you look at it and it's known to be the best out of all the 27" screens. So actually the computer itself is about $1200-1500 bucks.
You are splitting hairs with the monitor. Yes Apple makes nice monitors, but so does Dell if you buy their Ultra Sharp displays. I actually feel that the color correction is better on my Dell than my iMac when it comes to matching for print.
That system you posted is $500 more than the a very similar Dell system which comes with a number of add ons like touch screen and 16GB of Ram instead of 8GB. If you add the extra 8GB of ram and you have another $200+ on your system, so you're is much more. But anyone that buys an all in one is a idjit.
I would recommend buying a desktop system as you can get even more.
Here's a system with an i7, 32GB of RAM, 3TB ofHD + 256GB SSD and 1.5GB Nvidia and a 27inch monitor and a "Bluray burner" for the same price as the iMac which is an all in one that is not very upgradeable.
Or you could piece it together a bit more and go this way (see what I'm doing here? I have choice)
Same i7, 24GB of Ram, 2TB HD, The super fast AMD 7870 Video card, a bluray burner for only $1799
Then I can add a 30 inch monitor for $999 and still be close to the same price as your system for waaaaaaayyy more.
If I match spec for spec, your iMac system as a Dell desktop with specs as close as I can get it only costs me $1235.00. So even if I added an extra $500 just for snizzles and sheets I am only at $1735.
And for what it's worth, it's not always about buying the most expensive system. If I opted to buy a slightly cheaper system I could get even more value and still get a very fast PC yet the iMac would not be a lot cheaper.