iMac is probably one of the most "cost effective" machines in the Apple line. tbh, if you "need" everything it offers, the price is very competitive. ACDs are top notch quality, and a 27 inch retails for 1000. That leaves $700 for what's in the machine, which isn't terrible. That's not more than $200 overpriced in that sense, and for that, you get an all-in-one design [for better or for worse]. No customizing though, which is a real shame because that's one of the premier reasons to get a desktop: so you don't have to replace it every 3 years, you merely update the parts.
The catch: this is assuming you 100% NEED the 27-inch IPS screen. Imo, IPS has a very specific audience. There are very few people who benefit from it, but a lot of people who just want Apple this, Apple that. Apple really is a religion. Now, with that said, ACDs are the highest quality monitors I've ever seen.
However, 24-inch LEDs retail for under $190 now. You can get 4 of these and you'll end up with 360 degree viewing angle. Heck, get 5 and make yourself a fort.