This is that old finance chestnut. Two finance professors are walking down the hall and one of them spots a twenty dollar bill. He goes to pick it up but the other professor stops him and says "no don't bother. If there was twenty dollars there someone would have already picked it up"

Yes, people arbitrage away these anomalies, and make billions doing it.

My point was more that the arbitrage is not systematically predictable, not that the arbitrage doesn’t exist.

And that would make the stock markets accessible to fewer people, further widening the wealth gap.