excuse-me-sir
Explanation
The Joke
A man approaches another person with an overly elaborate pitch: "Excuse me, sir, would you be interested in wearing your moderate social views, inadequate personal hygiene, mundane interests, and subpar intellectual merit like a badge of honor? Would I ever!" He is essentially asking the person to proudly embrace their own mediocrity and ordinariness.
The pitch continues: he is selling a t-shirt that promotes the idea that real experience is preferable to book learning (something like "School of Hard Knocks" merchandise). But then it gets meta -- the salesman observes that this notion, which starts as an agreeable idea, somehow transitions from reasonable to the point where the word "unpolish" becomes a moral good. The concept takes something that seems innocuous -- valuing practical experience -- and extends it into anti-intellectual pride.
In the final panel, the customer says he wants to buy it but asks if it could be more forthright about its message. The salesman responds: "That''ll be extra."
The Humor
The comic satirizes the commercialization of anti-intellectualism and the "proudly average" consumer identity. It deconstructs the logic behind products (t-shirts, bumper stickers, etc.) that celebrate being uneducated, unsophisticated, or "just a regular guy" -- pointing out that there is a strange journey from the reasonable idea that book learning is not everything to the conclusion that ignorance itself is a virtue. The final punchline -- that more explicit versions of this message cost extra -- suggests that there is a market for increasingly brazen celebrations of mediocrity, and someone is profiting from it.