My understanding of the slang word “jack” is that it means “nothing,” or perhaps “a small amount.” Like the title of this entry, for example. “You don’t know jack” means “You know nothing about this subject.” “You get jack” means “You get nothing.”
Now, it’s been established that Batiuk has created his own world with its own
idiots idioms. The thing is, your own private slang only really works when there isn’t a real-world version. He’s usually safe in this regard, as no human being has ever uttered things like “solo car date,” “vendo,” or “bio-dad,” but people use “jack” in the context I mentioned all the time.
Here, it seems to mean “money,” at least as far as I can fathom Pete’s meaning. “Jack,” used here, is such a square-peg forced into a round-hole (forced with a hammer, while the peg is screaming) that I’m thinking it might get added to the Batiukionary.
Normally, in most strips with a *cough* joke like this, the drawing in panel three would be a slight variation of panel two, with the two halves of the *cough* joke implying a character’s single bit of dialogue in a single moment. But I like to think that Pete said his dumb first line, then silently struggled to shoe-horn “jack” into his next sentence while everyone else ordered, paid, picked up their coffees and headed toward a table.