Selling something with a flaw you didn’t mention isn’t a deal. It’s a lie with a receipt.

Deals only count when both people are looking at the same object. Leaving out the crack, the battery, the thing that only shows up after a week turns it into something else with a friendly face on it. Money changing hands does not make it honest, it just makes it documented. The buyer usually finds out, and what they remember is that you knew.

Say the flaw out loud before the price. Most people will still buy, often at your number, and you get to keep the reputation you would otherwise be spending.