It's a common rhetoric from someone who has no clue about financial markets (the person you replied to).
Suppose you want to invest in S&p500 so you want to buy the ETF. Someone like Jane Street can create sell you this ETF, and take care of the risk that comes along with it. For example, the price they sell you this ETF should take into account the pricing of underlying stocks. While it sounds trivial, doing this profitably (and therefore sustainably) is a tough job. And doing it competitively to offer you a good price on it is an even tougher job.
It'd make sense if you were writing out some Boolean expressions or trying to present something with formal logic. But you're writing English here so it seems inappropriate to a) ditch conventional grammar and b) pass off the criticism as "imposing their limited experience".
One thing I don't get is how they sustain themselves in terms of income - does anyone know what they do to support their lifestyle? Just really curious (and potentially out of the loop). Thanks.
Suppose you want to invest in S&p500 so you want to buy the ETF. Someone like Jane Street can create sell you this ETF, and take care of the risk that comes along with it. For example, the price they sell you this ETF should take into account the pricing of underlying stocks. While it sounds trivial, doing this profitably (and therefore sustainably) is a tough job. And doing it competitively to offer you a good price on it is an even tougher job.