Had the same debate with someone about it about 9 months ago. He claimed he can built the same spec at 50% of my iMac (£1980), so he had a budget of £960. So I challenged him, put his money where his words are and show me.
The truth is...he was cutting corners.
The machine he specced was loud, or at minimum, louder.
The machine was big.
It was not a 10 bit IPS monitor.
He didn't spec the Apple keyboard or the mice - I want these as I like these.
He didn't spec the OS
It had nothing like thunderbolt, or webcam.
Above all, his final cost came to 50% OVER budget, about £1400.....and had to built it himself and it was still not identical spec as my iMac.
People like that do not get it, they don't get you need time not to just build it, you need time to research, you need time to find the best price, you need time at home to sign for a dozen different items (as opposed to once for the iMac). They don't understand not everyone is as computer savvy, yes this is a computer forum so it's geeks abundance but the world out there is less so.
Majority of the time they see CPU Ghz speed, the amount of RAM and the graphic card, perhaps the HDD/SSD and compare to another computer with those 3 things. Everything else is ignored.