I don't think it would be using the EFC from FAFSA.... though I tend to get lost in FAFSA for MBA.
If you are admitted to GSB, there is a calculator on the Admitted Students site where you can run through the numbers and get a sense of how much aid you can count on...
Anyway, for GSB MBA, you would be a family of 1 or if you have a wife and children that would be your family size used for the calculation. They would look at your income and assets and then run it vs. costs. My guess is at 110K even though you pay a ton of taxes to Fed and State, you would be eligible for a little bit of aid (hopefully I am wrong and you get more). About 50% of GSB admits get need-based aid but GSB expects you to take a loan and contribute towards your cost so the amount of fellowship would be Total cost minus your expected contribution based on income/assets, minus a base number (likely 25% of cost).
Have you seen this one?