LukaBoki :
You're selling EVERYTHING?
An easy $2800-$2900 in your pocket.
That isn't really accurate. First off the biggest reason is the GPUs.
https://pcpartpicker.com/part/zotac-video-card-zt7050610p
You can buy a GTX 780Ti for $460 now, and no one is going to pay $700 for a used product that they can buy for $240 less.
http://www.ebay.com/sch/Computers-Tablets-Networking-/58058/i.html?_from=R40&LH_BIN=1&_nkw=780+Ti&_sop=15
You can buy several of them under $400 on ebay, so that is what you should expect to get out of them. So $3500 - $600, so right off that puts you at $2900.
The fans you can buy for $10 each on Ebay brand new, so no one will want to pay close to double for used fans of the same make and model. Minus another $14 for those at least. The larger fan you can get for $12, so thats minus another $16.
http://www.ebay.com/itm/Corsair-Air-Series-AF120-LED-Purple-Quiet-Edition-High-Airflow-120mm-Fan-/361100800827?pt=US_Computer_Case_Fans&hash=item541348f33b
http://www.ebay.com/itm/Corsair-SP120-Quiet-Edition-Air-Series-120mm-x-25mm-Single-Pack-/151436649512?pt=US_Computer_Case_Fans&hash=item234253e428
The display can be had for $450. Thats minus another $120
http://www.ebay.com/itm/Dell-UltraSharp-U2713HM-27-LED-IPS-WQHD-Mint-and-in-original-box-/331365647994?pt=Computer_Monitors&hash=item4d26ee867a
The Windows 7 license is likely a user license and not legally transferable from one person to another, either that or it is dependent to the system. Regardless no one will want to pay for it since OS is typically considered complementary with the system. Thats minus $100
The hard drives at best you should expect about $45. That is minus $42 each, so $84
http://www.ebay.com/itm/TESTED-Western-Digital-WD-Black-1-TB-Internal-7200-RPM-3-5-DESKTOP-HARD-DRIVE-/191400376256?pt=US_Internal_Hard_Disk_Drives&hash=item2c9059f7c0
The SSD minus $10.
http://www.ebay.com/itm/SAMSUNG-MZ-7TE120BW-840-EVO-Series-120GB-2-5-Internal-SSD-drive-418480-90-/281488178073?pt=US_Solid_State_Drives&hash=item418a00bb99
The RAM at highest you should expect $150, however the auction below isn't getting any bids for it. Reason is that faster RAM offers no value in performance. Especially when, in the other link, you can buy 16GB of RAM that has the exact same performance for $50 less. So minus $75 for this one.
http://www.ebay.com/itm/G-SKILL-Ripjaws-X-Series-16GB-2-x-8GB-DDR3-2133-Desktop-Memory-/171532722596?pt=US_Memory_RAM_&hash=item27f025a1a4
http://www.ebay.com/itm/G-Skill-PC3-17000-16-GB-DIMM-2133-MHz-DDR3-SDRAM-Memory-F3-17000CL11Q-16GBSR-/221598669983?pt=US_Memory_RAM_&hash=item33984f5c9f
Motherboard $116 Ebay. So minus $30.
http://www.ebay.com/itm/USED-MINT-ASUSTeK-COMPUTER-MAXIMUS-VI-HERO-LGA-1150-Socket-H2-Intel-Motherboard-/331362209748?pt=Motherboards&hash=item4d26ba0fd4
H100i, selling for at most $65 from Newegg, and even less used from people. So drop another $40 for that.
http://www.ebay.com/itm/CORSAIR-Hydro-Series-H100i-CW-9060009-WW-RF-Water-Cooler-/301380790906?pt=US_Water_Cooling&hash=item462bb1ea7a
CPU minus another $60.
http://www.ebay.com/itm/Intel-Core-i7-4770K-Haswell-Quad-Core-3-5GHz-LGA-1150-84W-Desktop-Processor-/321577624616?pt=CPUs&hash=item4adf852428
I didn't hit quite every part but I got the majority, and if you are following along that should give you an idea that someone could buy this computer and put it together in parts for $2341, with getting some of the parts brand new as opposed to used. So someone who really thinks this system is awesome might go for the $2300 range, but think what that gives them. They get a PC with used parts, that they paid a lot of money for and if it breaks, what do they do? Warranties are non-transferable and so anyone who buys any part of this thing and a part breaks, they are out that money and don't have the option to have repairs. So people will be weary of paying out that much money for a big pre-built system and will prefer to go through a trusted source. In addition to that, most who will spend this much on a computer know what they are getting into, and will see parts of this system like the RAM and fans as non-essential bits that just add to the price but are of little value, and likely will prefer to customize the system to their tastes. These factors will make selling this system at $2300 a fair sell, but a very tough sell that will likely be hard to get anyone to go in on.
This is why I keep suggesting that you should sell the parts and not the whole system. It will sell a lot faster. People won't be taking as large a risk buying a $300 dollar CPU without warranty compared to a $2300 PC without warranty. In addition selling the parts as separate pieces might allow you to pull some extra value out of the graphics cards and other pieces that people will want to build their own custom systems. That is a better idea overall.