I find it rather interesting that something like, "$5 million made by trading as GS, and you get to keep 30%" ....was said so casually. First off, those days are long gone, mid 1990's when the bigger firms were paying anyone that kind of money (except for the bigger partners). Their "traders" generally move money around, and are very limited as to what they can and cannot do. This can be a great job for many people...but not necessarily a great job for those who want to control their destiny. Massive layoffs have taken place in this part of the game over the last couple of years. Even the "employer type" trading firms have cut back a major percentage of their prop traders.
If you really think you can make $5 Mil (or even $1mil), wouldn't you prefer to keep all of it?
Just my thoughts...