Of course there’s no “perfect information” (why quote something I didn’t say?), just available information. The sentiment is that arbitrage opportunities are r

Of course there’s no “perfect information” (why quote something I didn’t say?), just available information. The sentiment is that arbitrage opportunities are rare and typically disappear before they can be exploited. Again, no one would claim that they don’t exist period — that’s the whole reason the joke is funny. Honestly, if you look around and see “unexploited arbitrage” then you should be wealthy. I don’t personally see many $100 bills as I walk around, to use the metaphor from the joke.