WWTOBD: returning used tires from eBay

I noticed some cuts near the sidewall on one of my tires (cooper zoen ltz AT tires) I've got a about 20k miles worth of tread left on this set. I checked eBay and found a set of used tires same make and size as what I had claiming "6/32" tread across the set" for $350. One new tire was about $250. I decided to pull the trigger on this set figuring they can get me to my next new set. The tires come in and have plenty of tread on the shoulders but on average there's 3 to 5 /32" across the crown with very few instances of 6/32" or better and plenty cases less than 1/16" . Well less than the 6/32" listed on the ad (I know it's 3/16" but that's how they had it listed so I'll keep it that way for percentages).

I send the seller a message on eBay stating the above with picture of my caliper showing the thread depth stating that I want to return them at no cost to me. He responded I could return them for a full refund but I have to pay to ship them. i told him no, he needed to send me shipping labeles. He responded "are we really arguing over a few 32nds of an inch?"

Hell yes we are! Assuming the minimum useful tread is 3/32", the tires are essently borderline useless. So my options:

•Pay for shipping and get my money back.
•Take this up with eBay regarding a misleading listing and turn in a negative review.
•Continue to try to work with the seller.

WWTOBD