I think people are being a bit too dramatic. When you take into account that to buy a comparable display separately would cost $1700-$2000, and the fact that there is pretty much no competitive all-in-one on the PC side, I'd call the 5K iMac a good bang for the buck. The XPS 27 $2199 model only comes with 32GB SSD +1TB HDD, a GT 750M, and no 5K retina display. There's simply no other AIO so well-rounded for the price(Screen, build quality, performance). The upselling sucks, but lets quit pretending that PC manufacturers don't do it. On the new Surface Book, you can't even get a 512 SSD or 16GB of RAM unless you get the top end $2699 model.
Now, the 4K 21.5" iMac is BS, though. There's no excuse for the lack of a dGPU BTO and a standard HDD. I'm severely disappointed and see it as a missed opportunity. They could have at least put the M380 in there or give it as a BTO option.