I've asked this on the PCGS board but if a First Charter $1000 came out tomorrow. What is it worth? I am NOT a currency collector but always curious. If one of the $1000 Watermelon sold for $3.3 million I think if by some miracle one of these turned up it has to be a $5 Million Dollar value right? Pure and total speculation but always cool.
From http://oldcurrencyvalues.com/1000-first-charter-national-bank-note/ : So, I would say at least $1M is safe. $5M would not surprise me.
I believe the vast majority of known survivors are in private collections and won't likely ever come up for sale/auction. So I would guess anywhere north of 2.5M would be a good starting point.
It is entirely possible that one could turn up sometime, but value is going to be determined on condition and where it was issued, without looking at the Kelly reference I believe just Boston and NYC had banks that issued them.