Run it through KBB and check the blue books.....and remember unless the tires are BRAND NEW, technically it cannot be in MINT shape, it must have new or like new rubber for that, any tire wear makes the condition good, or excellent if they do that, but MINT requires OUTSTANDING rubber...and large amounts of mods or aftermarket add ons actually detract from value. If you are using OEM Add Ons professional buyers will give a lean to the add ons if they are OEM and installed at dealer with receipts.
As much crap as I hang on my trike, at the end of the day, I know it will likely cost me value at resale. If it has a modded or aftermarket exhaust or intake, try to get the original parts if you are paying for an excellent or mint machine.
Just some wheeler dealer advice, I have purchased and sold over 200 machines over my riding time of 40 years, and I cannot resist a flip, so play it smart, and stick to KBB values...IMHO if a NADA value exists, they are not really relevant to MC's and I typically use KBB as my guide. I recently purchased my RSS, but I would not pay 18500 for the ST, even newish like that, but thats me, and I have not seen the bike.