As a very wealthy player, Ive decided to contribute once again with some very useful information.
Recent updates have made it easier to track the prices of all in-game items and materials.
The following images provide a list of the most common items on the general market, along with their current unit prices.
There is also a personal ranking system based on highest prices and speed-sales.

You can draw your own conclusions about how to become rich- ... I mean, about how many advantages you can gain from this board. 😉
Have fun!