I think a simple way of explaining Store of value is that it is effectively referred to something that has intrinsic value in itself which is what gold or silver is and that value is not linked to something else. :)

Oh btw, Judas betrayed Jesus for 30 pieces of silver my friend.. or atleast that's what the book states (of course we can't be too sure, since some of the money might've been black that was unrecorded ..lol)