[He cannot help but laugh again at her antics, a chuckle that bubbles up between his own bites.]

Hence the advertisement, I assume they know not all will become their patrons in full.

[It does occur to him that as a newcomer, she might not know how to gain stamps - or any other kind of currency here.]

Though it may not be your intention, you are not incorrect. Such an act would earn you the ability to gain currency here, in the form of stamps - collect enough stamps and one may purchase almost anything one may wish.