Today they made 12M US$ volume. At 0.20% fee that's an annualized rate of 8.6M$ of profit. That should buy enough servers to handle legit or illegit clients, depending on how powerful the other side might be.
They probably make 5-10 times that by manipulating the market...
Like engineering 10% price swings every few days.
They are a monopoly...
And they are not making squat on those "low" fees...
Read between the lines.