We are talking a couple thousand gold worth
We are talking a couple thousand gold worth of investment right there if you do not mine it yourself. Its basic logic though lets say you invest 2000 Maple Story mesos to become revered with the Thorium Brotherhood. You learn how to make the revered epic items.
Congratulations you are probably one of the 0.01% of the people on your server than can make them. And you know what? 99.9% of the people on the server want those items because they are some of the best gear/weapons in the game!
There is one guy on my server that makes weapons for 4000-5000g each. It does not take a math genius to see that the return on investment can be very lucrative! Some of you will say Oooh but Gen how in the hell am I supposed to get 2000g to invest in this?
Well, you could either plan ahead or mine the dark iron ore yourself (for Thorium Brotherhood, for the others anyone can do it), or do what I did and sell what you can sell like a madman and save!
You do not go to Las Vegas with 20 bucks and expect to win thousands of dollars do you?