Ranger: "I take the armor to the blacksmith to sell. How much does he offer?"
DM: "Roll me a couple d20s". (The DM intends for the first to be an insight check and the second to be a perception check. Insight to read the blacksmith's reaction, perception to just notice the ring and gauntlets).
Ranger: "Why?"
DM: "Ability checks."
Ranger: "Which abilities?"
DM: "If I wanted you to know that, I'd have told you." (Sticks out tongue).
Ranger: "17 and 4 on the die. I don't know what to add to them."
DM: "I do." (DM rolls a deception check for the blacksmith and gets an 8 - much lower than the PC's 17+1 Insight) "You step into the blacksmith's shop and are surprised by how clean it is. Instead of soot and grime, it is spotless and smells of lemon. You notice a cloth casually floating along a windowsill dusting by itself - a sign that this blacksmith can afford a magical servant. He is a middle aged human with a well-muscled frame and a grim demeanor ... at least at first. As soon as you drop the armor on the table and offer to sell it, his eyes nearly fly out of his head. He is clearly very interested. He immediately offers you [the fair price for the armor]."
Ranger: "Is that a good price for the armor?"
DM: "Roll an intelligence check."
Ranger: "18."
DM: "You've heard tales of a similar suit being sold for slightly less than that, but that was some time ago and far away. You might find someone willing to offer a bit more somewhere else, but it seems in the right tourney field."
Ranger: "OK."
DM: "He is practically salivating as he asks if you have a deal."
Ranger: "Yeah, I guess."
DM: "The blacksmith is trying to contain his excitement, but you can tell he is extremely happy. He runs to the back of the shop and returns a few moments later with the funds in platinum. He places the coins on the counter for you and then grabs the armor. As you turn to leave, you see him start to inspect each part of the armor in detail, mumbling under his breath as he does so."
Ranger: "Good for him. I grab the coins and go."
DM: "Roll me a d20."
Player: "Why?"
DM: "If I wanted you to know...."
Ranger: "Ugh ... 13."
DM: "You heard him mumble that THIS is going to make it so much easier for him to work faster."
Ranger: "Huh? Why is armor going to.... Never mind. More power to him. Weirdo."
DM: (Rolls a die for no reason): "He doesn't even seem to notice you leave, much less note your disdain."