support for the theory
It's funnier
Get it? People are only “buying” “pictures” of Claudius because it’s the coinage.
It's cleverer
So — if one interpretive choice is that Hamlet is reciting the dry fact that people are buying Claudius’s picture, and in the other, he is mocking the fact that people buy Claudius’s picture only in the sense that they use coins bearing his picture as a medium of exchange, then which makes for a cleverer Hamlet? Why not give Hamlet and Shakespeare the benefit of the doubt, and enjoy the line as one more biting insult?
It is echoed in other lines in the play
Get it? Bats use echolocation.
The picture in little line, the counterfeit presentment scene, and the “king’s countenance” jab all echo each other, IF they all refer to coins.
If Hamlet is using coins in the “counterfeit presentment” of two brothers where one is “blasting” the other like a “mildew’d ear, and where the Queen says the ghost is “the very coinage of your brain”, and if Rosencrantz and Gildenstern’s “soaking up the king’s countenance” means they are accepting his coin, then everything is better if Hamlet has already introduced the fact that Claudius’s picture is, in fact, on the coins.
It's just more like Shakespeare and more like Hamlet
It’s not like either of them to miss an opportunity for a pun. Are we really going to assume no pun was intended?!