Roughly 30 - 40% more than you could expect to get working as a programmer outside of finance. But considering that the hours are longer, it's not much more on an hourly basis on a straight salary basis. However, if you're an employee, you can also get substantial annual bonuses.
Bank in the 90s I worked for a small derivative shop in NYC. The lowest bonus we ever got was 100% of annual salary. This was not a boring project either - we had a network of Suns and all code was written in Eiffel and C.