An interesting table showing how much JP Morgan makes per trade on average, broken out by different trades.
A few interesting points:
1. There isn't much money in equity trading. It's a high volume low margin business.
2. Swaps and loan deals are much more profitable but probably require more effort to put the trade together.
3. Most of JPM's revenue comes from fixed income. Students who are interested in investment jobs take note - the action is in the fixed income business not long equities.