My question though, is no matter what their methods, retails or professionals if we all are profitable, who are we taking our money from?
In quant terms, professionals bet on the "risk neutral measure" and the retailers use the "physical measure". Ajacobson's example is an example.
You can equate "physical measure" with "stock direction" and "risk neutral measure" with "volatility". Two problems:
1) Stock direction is way more difficult to estimate than volatility (mathematically the volatility is "signal" and direction is "noise"). If you estimate it wrong, you lose. Same happens with volatility, it's not just "the spread" as retailers blindly repeat some half baked trickled down quant knowledge. Estimating volatility has it's errors too and if the spread gets too narrow, there are good chances they'll lose money.
2) Direction only works one way, volatility doesn't care about direction. In Ajacobson't example, the market maker would have made money also if the stock moved the other way. The retailer would have lost money.
So the correct answer is: options trading is a zero-sum game between directional option traders (a.k.a option gamblers) and the stock market (blissfully unaware of the derivatives world above them). The market maker (a.k.a. option arbitrageur) is the intermediary which, under ideal conditions, always makes money. On the other hand, the retailer are just gamblers: they may win or lose, the money comes or goes to the stock market, minus market maker's "spread".
By the way, anyone calling themselves a quant should know this.
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