The Teller

The Teller is is head of the Transmutation Bankers, the person who determines the value of every valuable and good in regions under the Bank's influence. Since slight fluctuations in the market can devalue certain magical components that are needed for spells, it is critical that the value of those components remain at a constant or near-constant value else a spell could fizzle in a moment of dire need.

No one knows who the Teller really is, or if there have ever been a changing of hands when an older teller passes on the responsibility to another.

Theories
Some say that the Teller is a God, elevated to mortal omniscience for just this purpose, some say the Teller is actually an infinitely complex machine, calculating and watching somehow. Another theory is that the Teller is actually a great diviner, able to see and track every resource on the plane.

One thing is clear, whoever the Teller is, its a much preferable option than the 'March of the Modrons'.