That's not how it works. People pay those prices for old parts on individual basis. For example if their LGA775 C2D CPU failed they might get a cheap Q6600 or maybe they want a cheap $100 upgrade for their E6400 system instead of going out and buying a brand new $600 PC, or maybe they got a free Q6600 CPU and DDR2 but need an LGA775 motherboard since theirs failed!
No one who follows PCs would actually go out and buy all those parts 1 by 1 and pay $540 for them.
Also, you say your motherboard has 3x PCIe slots. Ok what for exactly? A Q6600 @ 3.6ghz bottlenecks single-GPU videocards 2 generations ago. Either way if your friend paid $500 for that system, your gain, his loss.
Me neither. If any 1 part breaks in that system over the next 3 years, you would have to pay $50-60 at least to replace anything there other than the RAM. I'd rather spend $600-650 on a brand new system with a 60GB SSD for the OS and a modern power efficient 2500K+ OC and 3 years warranty for most new parts. The system presented by the OP has no warranty after 6 months, no SSD, none of the modern USB3.0/SATA3.0/USB smartphone/tablet charging features, and uses extremely power inefficient components that will add up in electricity costs over time. The electricity costs alone over the next 3 years are going to wipe out nearly $100 in savings today. Not to mention, a person who is a "power user" will not be able to survive with 4GB of DDR ram. Actually for a power user a system with only 4GB of DDR and a mechanical drive for an OS is already a non-starter. 99% of people who have an SSD for their OS / apps would not be able to go back to the "chugging" mechanical drive.
Even Anand discusses this in great detail in his
First Podcast. He even goes on to imply that even a tablet is snappier than a $600 PC without an SSD.
What VL doesn't realize is that in games that are not multi-threaded (most games don't use up all 4 cores yet), the Q6600 @ 3.6ghz is only about as fast as an E8600 Core 2 Duo, while in multi-threaded apps, an X6 1045T @ 3.8ghz CPU has ~50% more performance since the 2 CPUs have similar IPC. The Q6600 is worse than an i3 for games and worse than an X6 for multi-threaded apps.
Finally, the person buying the system is sinking $500 into a hole. What do I mean by that? In 2-3 years, you can still resell that $650 system with Core i5 2500k + 60 GB SSD, Z77 motherboard, HD7770 GPU for at least some $. The actual cost of ownership cannot be minimized in this case since you cannot recoup much in the resale value of system on a Q6600 processor should you want to upgrade in 2-3 years from now. That's another aspect that was totally ignored!