Existential Crisis: What is Mint? Does it Exist?

One of the most confounding things about the hobby is condition. My way of dealing with this is just buying what I want/can afford without paying too much attention to whether or not it's "gem mint." I just use closed sales on ebay to gage what a card in similar condition usually sells for and make my bids accordingly. That's fine for buying.

But selling? Selling is another game, friends. I've had to sell off large parts of my collection over the past few years and have seen a lot of shenanigans on the part of buyers who are looking to scam sellers (never thought I'd say that). The one I'm most afraid of is the innocuous question: "Is the card mint?" 

First, as has been hashed out by millions of folks on the intertubes, condition is 100% subjective, even when Beckett and PSA sit down to hand out grades. There are guidelines, but whether or not a given card meets those guidelines is up to the "grader." I'm no power seller and don't care about condition for my own collection, so I usually just say cards are "pack fresh" or "see scans for condition."

Second, the cards in question are from 2000-on and never go for more than $10 or so. We're not talking vintage kept in a shoebox in someone's attic for 50 years. These are "new" cards in solid condition that have never known the joy of Timmy's bicycle spokes. People understandably want their money's worth, but anyone who has ever opened a pack of Topps Heritage knows that 99% of the cards out of the box are not, strictly speaking, "Mint."

Third, I would think that if you have to ask about basic condition that would be a signal that this auction isn't for you. Just a thought.

Which leads me to this: rather than being a sincere query, I see the question as usually a prelude to some combination of post-auction payment reversals, card switching, and complaints about the listing. 

So help me out, just in case I'm completely misreading a small portion of these folks. Mint? What in God's name is passable mint in the great market place that is the ebay? Is no creases, well-centered, but with a tiny chip on the edge Mint (it's a 9.5 Gem Mint according to my David Price)? Or is that card NM? How about a perfect card with a small printing mark on the back? Or a card whose only flaw is a splotch of stray ink the size of an amoeba which is only visible through an electron microscope?

I honestly have no idea.