And here is how it played out in an alternate universe:
On the drive up the guy texted me this:
Buyer: "Would you consider $550? Haha thinking about turning around this traffic is horrible."
Me: Sorry, I think it is worth $650. I agreed to honor the mistaken $600 price. Can't go any lower. Up to you what you want to do.
Buyer: Figured you'd say that, just checking. See you in 45 mins.
Me: Cool. Drive safe.
<60 minutes later>
Buyer: Damn, dude, this bass is awesome, thank you so much! Keep my number and let me know if you ever have anything else you want to sell.
Me: Sure thing buddy, will do. Thanks and enjoy it!
Buyer: Oh, by the way, my little sister is a supermodel, and her lame boyfriend just broke up with her. You seem like a really nice guy, and you look like her type. Are you single?