I think it is a legit question to ask. It is very difficult to answer, but the question is legit. I can understand that someone would want the answer to this question, because at first glance, it is indeed weird how expensive Macs are compared to PCs.Could we all stop feeding this troll please?
I recall building my own PC years ago. What I then noticed was that the cheaper components often were closer to the limits of their specs. All these edge-components together would create impossible to debug problems.
Comparing an iMac to a self-built PC is almost impossible. Because there is 4GB RAM and 4GB RAM, but it is not the same, even if it is both DDR3 etc. E.g. cheaper stuff may run a bit hotter, as a result your fans will be louder. Important? For some. Is it part of the superficial comparison of specs? No. And nor is panel quality when you say "full HD screen" (question: if it is 23" full HD, are your icons and stuff still readable?). A BluRay looks nice, but what if you cannot use it to display movies on your separate monitor because of DRM issues?
But it remains a legit question. The only thing I can say is that most serious analysts that I have read about this question have concluded that Apple hardware is not outrageously priced and that you get a comparable price/performance. Sometimes it even turned out Mac was the cheaper option. You may not need all the stuff Apple puts in (e.g. Firewire800), so you may pay for stuff you do not need. But IMO, you do not pay for the brand/image per se.