Much of the activity of Wall Street and City of London traders in investment bankers constitute a form of rent-extraction. Their phenomenally lucrative market-making activities in interest rates and foreign exchange don’t actually create new wealth – they merely shift money from the pockets of companies and pension funds into their own.
In a properly functioning market new players would enter and these outsize market-making profits would be competed away. But the sheer size of these financial dealers erects effective barriers to entry, curbing competition. And the “too big to fail” status of these mega financial institutions (which provides an implicit state guarantee) also secures them artificially cheap finance in the money markets, compounding their commercial advantage.