The iMac Pro starts at $5k, but only it comes in Space Gray, Apple's closest offering to black. The same's true of its peripherals, which are not sold separately. If you like, you can buy a Space Gray set on eBay for $1,525 — with an hour of bidding to go. [via @mathowie]
Only the Keyboard, Mouse and Trackpad. These are the dark ones that come with the iMac Pro and cannot be bought any other way. Unused. I already have a preferred keyboard/mouse combo I chose to use for my configuration and won't be needing these.
Or, just get a perfectly-decent Matias knockoff for $100. (Amazon)
Update. SOLD for $1525, with no further bids.