In a burst of EXTREME (like, totally extreme) irony which no one will ever hear about except right here in this narrative, when Liam still called himself a Hollow One he also called himself Dust, as in ashes to ashes and so forth. Because he was 16 years old, and that is the cleverest time of all in a young man's guyliner-smeared life.
"Hey. 's 16.50." Please at least pretend to look at the cash register, Liam, and also like it did not just take your typist a half hour to add that up. In the idle, useless snap judgments he makes of everyone, he wonders if Sebastian is high, and also chooses to ignore the 'possibly not human' vibe, because there have been enough of those in the store tonight thank you. So this works out for everyone! Sebastian can pretend to be normal, Liam will pretend he is, everyone wins.
"Those are buy one get one, if you want." The ice cream, specifically.