400$ would be a fair price
Sorry, but no it wouldn't. This is an older system with just basic components. You can buy this whole system brand new for around $500, and it would all come with new warranties. $200 would be more realistic. But I would only pay that if I got to see the system in person before I bought it. I would never buy a used computer online without seeing it for myself first.
PCPartPicker part list:
http://pcpartpicker.com/p/W7TjwP
Price breakdown by merchant: http://pcpartpicker.com/p/W7TjwP/by_merchant/
CPU: AMD Athlon X4 860K 3.7GHz Quad-Core Processor ($76.98 @ Newegg)
Motherboard: Gigabyte GA-F2A78M-D3H Micro ATX FM2+ Motherboard ($64.61 @ Newegg)
Memory: G.Skill Ripjaws Series 8GB (2 x 4GB) DDR3-1600 Memory ($29.99 @ Newegg)
Storage: Western Digital WD Blue 500GB 2.5" 5400RPM Internal Hard Drive ($47.99 @ Newegg)
Storage: Western Digital Caviar Blue 320GB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Newegg)
Video Card: XFX Radeon R9 280 3GB Double Dissipation Video Card ($173.98 @ Newegg)
Case: Corsair SPEC-01 ATX Mid Tower Case ($49.99)
Power Supply: EVGA 500W 80+ Bronze Certified ATX Power Supply ($38.98 @ Newegg)
Total: $532.51
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-01-14 21:00 EST-0500