Mona Lisa on 2 Colones, Banco Internacional de Costa Rica issued banknote - How much this banknote worth today in XF or UNC condition? http://latinamericanbanknotes.blogspot.com/2010/11/mona-lisa-on-2-colones-specimen.html
It's not a banknote. It's a specimen printing. That might make it worth much more than an ordinary piece of currency, but I don't know enough about it to say so.
In this case the specimen notes are much more common in higher grade than the issued notes. Banco Internacional was absorbed by the Costa Rican Central Bank in ca. 1944 and all their notes were called in and overprinted. As a result they are fairly scarce - particularly in high grades. There is a lot of interest in the notes because they are the only notes with the Mona Lisa portrait on them. It is an enigmatic issue, one does wonder why Mona Lisa was chosen for the note other than perhaps a bank official was an art afficianado.
Human faces are an excellent subject for banknotes, because we are evolved to notice the slightest differences among them. The person who decided on the subject of this note was probably an aficionado of both art and people. Which, upon reflection, is basically the appreciation of both.
I would tread carefully on eBay as these notes are significant enough that there are likely copies of them out there.