The humor in this meme comes from the contrast between the expectation set by the user's praise and the low cost mentioned, against the actual quality of the tattoo, which is a poorly executed rendition of what appears to be the Joker from the DC Comics. People might find it funny because tattoos are expected to be high in quality due to their permanence on the body, and this meme plays on the discrepancy between price, expectation, and outcome.