well, there were plenty of single character .whatevers available to register, all with a variety of renewal fee's.
some low $$ to $,$$$, per year.
so, until either you find a buyer or wait for one who can pay the amount you ask, then the current value is reg fee or.... whatever actual dollar offers you get, above that.
but in theory, if reg/renew fee is $400, then next year, it's worth $800 and year after $1,200 and so on and so on, until you sell.
as is, there is no established market, outside of "registering them from the registrar" or wait for when they decide to release their reserved lists of "premium" .whatevers by auction.
from that, i'd say value of your name could be seen in comparison to.. "average closing prices for similar single charter .whatevers", calculated from various venues.
however, even in such environments, closing prices are affected by frenzied buying, which may not exist outside of that bubble.
imo....