About goncourt, do one of those guild training rooms. It only costs level x 10g and can get you 20+ book boxes. Lots of profit there if you have the patience.
I also find PvP to be a healthy source of cash, I get about 3 mil every tournament, and I lose half the time. Not to mention the 100k exp book that you can get (div 9 + i think?)
Also, I thought I should mention the arena ^_^ money drainer a lot of the time, but smart betting can give you a profit almost every time, even though it might only be 10%.
What is the definition of rich? How much do you need to have to be considered wealthy/affluent, etc? I'm just trying to get an idea of what to look out for, what sort of plans i should be making around saving money, etc etc etc.
You can consider yourself rich once you have 1bil gold ^_^ + mercury + a couple of +10 equips =P
At lvl 90+ you have dungeons (indie, guild, nation) USE THEM and voila, thy art rich bugger.