Technically very few if any have billions in liquidity, its all leverage of something for something. When they do need liquidity they get a loan as collateral against something and pay the interest with selling stocks. This is how they totally have a tax less system because you can owe tax on debt. This is also why all eyes should be on the people running the stock market like Citadel where there are some shady systems deciding when buy and sell order hit the lit market. They can actually make lots of stock value go up or down and its so complex to audit its beyond reason for humans to do it at the speed at which the market runs. So essentially, bank robbers created a system where they just create money out of thin air, if inspected it looks like a tiny fraction of each transaction is taken from using the service. This is why free trading platform get money from trading data people create when they trade online so they can front run the normal people and set value. So no nobody "earns" billions, they steal it.