> oil market is, to put it mildly, fucking huge

Sure. But these aren't trades in "the oil market." They're bets on Polymarket and a specific oil-futures exchange.

For sure, the real trading markets are huge. I mean the betting platforms.

Are you implying that there is arbitrage between the prediction market and the real market? Until now we were assuming that the prediction market is self-contained, with its other side staying within the confines of the prediction market.