Nobody talks like this.
Now, I don't expect a great deal of naturalism in the comics section. There is something of a conceit embedded within the whole construction of the set-up and punchline joke. But I do think that the dialogue should make a little bit of sense. And it really doesn't here.
If someone were tell you that their business was back in the black, you would not reply with a flatly declarative statement of definition. A normal human being would probably congratulate them. But for the sake of this joke, Cosmo could have said something like, "So you're making money again, huh?" Or, even better, he shouldn't have to said anything. But instead we get the dictionary definition, as though the cartoonist just couldn't trust his audience to understand what "back in the black" usually means without him explaining it for us very clearly.
The difference between "So you're making money now, huh?" and "You mean you're making profits again" might seem small. But it's not, really, and it mostly has to do with the question mark, which softens the inflection of the line, but also with the way the construction of the line is turned around and made less formal. It's the difference between a reasonable approximation of naturalism and a line pulled straight from a dictionary.
This comic consists entirely of a couple of characters sitting around talking. And it's really good. The punchline doesn't even have the rhythm of a punchline. It just sounds like a thing TJ would say.
