My iMac is: iMac (Retina 4K, 21.5-inch, 2017) Intel i5-7600 3,5 GHz 32GB of OWC Memory (2 x 16GB PC4-19200 DDR4) Radeon Pro 555 2 GB OWC 1.0TB Mercury Extreme® Pro 6G SSD + 256GB M.2 SSD How much can I get from selling it?