"consensus that sellers will sell to whoever they want"
LOL. I have Told SEVERAL they can't afford something that I'm selling, whether it was at a Bash or a Swap Meet.
Their Attitude/LOW BALL offer & I refuse to sell the item[s].
Once I was offered $3 for a qt can marked @ $5. As the guy set the can down & reached for his wallet, I STOMPED the can. OK, NOW it's worth $3.
Some times it's fun being a Dick!
Can I recommend getting a GoPro video camera and start recording this kind of stuff... I might even pay to see that! would love to see that reaction