I like domain hacks, and I like banknotes, but wouldn't bet that the domain "banknot.es" is going to be redeemable for much more than the twinkle in your eye when you regged it.
Interesting -> Google returns 3,000,000 results from search on "banknotes" proper ... But do a search on "banknot.es" and I'm sure you'll be thrilled to find that a reference to this thread is one of the just 106 results returned ...
Domain hacks may be best done just for fun and possible development rather than driven by any expectation of $ returns from "traditional" domaining strategies. Maybe there are some exceptions to that rule, but "banknot.es" probably isn't one of them. It's a decent hack, but (in my opinion) not likely much more than that on its own ...
Well always a chance it will catch the eye of an end user with good taste for domain hacks ... And of course odds are better than even that I don't really know what I'm talking about with regard to likely value of this one - anyway, good luck making bank on your "banknot.es" ...!