My take on it is this:
1. You just get lucky. Through an expensive item drop, or a favorable crafting result, you manage to hit the jackpot by chance.
2. You trade your way into it. Buy low, sell high. Or, you managed to predict when nerfs are going to happen and bank off legacy items. Don't forget about the race rewards either, as you can use those to build up wealth.
3. You run "enough" bots to make #1 more likely or #2 more easy with more things to trade with.
Other than that, this game is not designed in a way the average person will ever be able to accumulate serious wealth unless they invest a lot of time into it and work for it. Botting obviously carries significant risks if portions of your wealth get wiped out.
I think if you dedicate yourself to building wealth, you can certainly do it, but it just depends on your real motivation and how much you want to invest (time, money, patience) to get where you want to be.