Saw this today for sale for $1000
($785 US)
Intel I5 2400 3.4ghz Never overclocked
$133
MSI GTX 1060 6GB Never overclocked
$270
16GB Ram DDR3 RAM
$140
128gb SSD Samsung 840 Evo
840 EVO 250GB is $90 on amazon
500gb WD Black Harddrive
$63 new, $50 cert refurb
700 Watt Coolermaster Power supply
$70 similar corsair, bronze cert.
3x Red Fans intake fans
in case
1x Out take fan
in case
Case: Cooler Master Masterbox Lite 5 RGB Mid Tower Case
$88
Computer Works perfectly
Full Windows 10 Pro
~$80 OEM
TOTAL: $934 without shopping much
IMO, I wouldn't buy a used system for 16% off of the price of the system brand new.
When I sell my mobo/cpu/memory, which is very comparable to that set up (see signature), I'll do it for under $200 *total*. It's always been well kept, clean, never overclocked, but the fact that it's used pc hardware drops the value just for the fact of it alone.
Might offer $500 ($637 AUS) for the system, maybe $550, but no more IMO.