So I just put together two used PC's. One is 25$. It's running an E8400(Dual core clocked at 3ghz) 2gb of ram, and a GTS 250. I was able to pick up a T3400 for 5$, which had everything but a half decent GPU so I put in a GTS 250 that I got for 20$. It can run CS:GO, 1080p just about maxed out at 60+FPS all the time. The other machine I'm putting together is one that would be hard to do. I was lucky enough to get a 7950(equal to a 760) for 55$(usually 130-150 on ebay) I had two old lga 775 motherboards laying around and I put in a X5450 because I ordered a few sticks to allow it to work on LGA 775 boards. I have it overclocked to 3.4ghz, I'm going to wait until I have a better cooler on my CPU until I bring it to 3.6(ish). Right now it only has 4gb of ram, but 16GB of ram is coming in the mail. that computer I'll be spending just about 100$ on. Right now I'm tossing the 25$ one on craigslist and going to be using the one with the 7950 as my main machine.
I quite often buy used components, the trick is not to get sucked into ebay bidding wars and to keep an eye on sites like CEX which provide a warranty.
I have found that components that might have been overclocked are best avoided, Intel k series CPUs can still be pretty expensive and might be screwed from improper oc's, same for fx8350's etc. Now that bitcoin mining gas largely passed buying second hand GPUs is also pretty safe.
My server(s) are all second hand machines. I was using a P4 but I recently got a Xeon X3320 Quad core and a Quadro FX1800 for free. It didn't have ram but I had 4x 2GB ddr2 dimms so I just need to get it set up now.
Half of my system is build with used parts... The hard drive, the CPU cooler, the keyboard, the fans, the ram.. So no. I never thought about getting used PC... Just the parts...
I have a problem with that spreadsheet. The 4850, GTS 250, and 9800 GTX+ are not what would be considered 1080p cards in any capacity. Sure, they are cheap but they really don't support any modern technologies and lack either memory capacity, or memory bandwidth.
Substitute those for DX11 counterparts at relatively the same cost: Radeon HD 5750, GTS 450, and let's say GT 640.
Actually no because I build a whole system about every 5 years so I need to go with new and reliable parts that have never been used before. I might want to do that if I want to build a new machine every 2 years but I think that would just hurt my wallet, even if I were buying used parts. Also, to be completly honest, an average user like me can go a really long way with a strong CPU + MoBo combo and just swap videocard when needed and adding RAM if needed.