There are ~8000 banks in the US alone, around 15K around the world.
According to your made up number, it costs $6K/year to run a bank. That's not even remotely close. That would pay maybe a month of the desk clerk's salary + overhead.
Fort Knox has basically nothing to do with the modern U.S. dollar financial system.
The U.S. dollar isn't backed by gold. The total value of the gold at Fort Knox, about $100 billion, is negligible [1] and does not appear on the Federal Reserve's balance sheet [2]. It is mostly an anachronism from the eras of the gold standard.
[1] https://en.wikipedia.org/wiki/United_States_Bullion_Deposito...
[2] https://www.federalreserve.gov/monetarypolicy/bst_fedsbalanc...
In the case of bitcoin they aren't inherently necessary to the function of the system, although with the risk of hacks you can make the case for them.
And since we're taking into account all of the underlying systemic costs going into banks, we need to do the same for Bitcoin. That means including all of the power utilities, factories, and mining facilities that went into making the hardware, plus the cost of shipping the hardware worldwide, plus the cost of the utilities and transmission lines needed to operate the network. And that's clearly not 1/20,000th the cost or resource usage of our current financial system.