What did you pay for it new? Knock 40% off that number
It's an end of the life platform component that had a refresh model. I'd knock another 5-10% off
Missing the I/O?! I'd pass on it for that very reason if I were a buyer lol. I'm meeting a guy today to sell a 4670K - Z87 mobo - and 8GB 1600mhz for $300 even. The older platform, the less retained value. I see 2600K/2700K with the asking price of $150-250, insane. Unless you get lucky enough to line up a buyer that's waist deep in desperation, I don't see premium prices flying.
I'd think of it this way. Z87/97 & Z170 A boards dance(d) around the $139-160 range. Boards that were and are more expensive than these typically have(had) more bells and whistles. Inclusion of, or extra 3.0 ports. Or now 3.1 ports. More sata ports, higher bandwidth this and that. Better intel or Killer network etc etc etc. The older the platform, even if a higher end board in it's day, the bells and whistles really aren't impressive anymore simply because they're standard now.