Tough to say what would be fair, as excellent condition might be somewhat subjective from person to person. I can tell you from my recent experience that there will be things, and maybe more than a few, that will need attention after the purchase, especially if you're not familiar with this particular make and don't know what to look for or ask about.
I wish mine was just a matter of turn the key, kick, and ride, but it wasn't. I thought it was in very good to excellent condition and it probably was, but I still encountered little surprises along the way. All of these surprises will cost you money. I'd say expect anywhere from $4000-$6500, unless this is a primo bike and then they'll expect more money back to recoup what they put into it. After buying it, ??? If you do buy it, only replace what you have to at first. That's my advice, anyway, for what it's worth.