[flourpower]

If you buy 100 dollars of mortgage bonds at a price of p and I buy it from you at a price of q, then your profit in that transaction is 100*(q-p), not 100. Besides, if you look at the profits made by investment banks since 2008 you'll see that they're nowhere close to trillions. Even the most profitable investment bank in the world, Goldman Sachs, had a total net income in the last three years of less than 25 billion. But your implication was that they made trillions as a result of what happened in the financial crisis, which is an even stronger claim.