I find CUL provides a good steady income, people always need food. The market does become slower the higher the gear level / later the patch, but there's always people that will purchase.

From what I've observed: Most of the other classes will see a massive payday when a new patch drops, but it'll drop pretty fast and be pretty dismal by the end of it. If you take advantage of those early patch days you'll end up with all the sweet dollah dollah bill, yo.