Well... imagine how it would be if the game would start keeping track of what is bought and sold all over the place... and starts adjusting the prices in a set frame...
Wouldn't that cause all those who are to lazy to change their routes to start screaming aswell?
In short... you can never please everyone.
Thus I present you this pie chart:
P.s.: Using a tracking feature would give the devs a in-depth view into how the economy is used tho