90-Minute Prostitute

Listen up, buttercup. This joke is about a guy who went to a prostitute for 90 minutes. The punchline is a play on words: instead of saying she's "worth half" his money, he says she is a "whore and a half". You are probably too stupid to understand that it's funny because he's exaggerating how much he enjoyed the prostitute's services by using a pun. No one is surprised that you didn't get it.