Does "that's that" always mean "end of discussion"?

Question

I have started a question in the sister forum but that didn't get much respond and I take it as a satisfactory answer at that time but I stumbled upon this example of use.

The two men both looked thoughtful as they silently walked back to São Romão.

"And if I hired you," the tavern-keeper said after a while, "would you come and live here?"

"Of course! Why should I stay in Cidade Nova if I’m going to work here?"

"And you’ll eat at my restaurant..."

"No; my wife’ll do the cooking, but she’ll buy groceries at your store."

"Then it’s a deal,” João Romão declared, convinced that this was no time to pinch pennies. And he thought to himself; “Those seventy mil-réis will end up back in the till; it’ll all stay in the family."

"So that’s that?"

"That’s that!"

The "that's that" in this example seems to best to replace with "that's it" or "that's all", as in this situation it just means "is it everything about the generous deal?". It contradicts with the answer in ELU that "that's that" has to be used derogatorily in a situation that a person feels that this is all he can do or take on the situation. Is this a correct use of the phrase?

Answer 1

"That's that" can generally mean "that's all" or "that's the end", or even "that's it", in the sense of "that's how easy it is".

If someone asks you how to make a cake, you might give them all the instructions and then say "that's that!", as in that's all, that's the end of the process, and that's how simple it is.

Of course, it can also mark the end of a discussion because of the "that's the end" meaning: "No you can't go to the party, and that's that!" Looking at the previous question, "Today's lesson will only cover the introduction about the course. And that's that" seems to have more of this kind of tone, so it would be better there to say "that's all" or "that's it". But of course it also depends on how it is spoken: with a big smile, "And that's that" would seem perfectly appropriate, whereas it seems harsher in writing.

Answer 2

The phrase "that's that" does generally mean "the matter is finished", but its use is not restricted to cases where you're trying to end the discussion. All the following uses are possible:

You're grounded, and that's that! [the matter is finished = that's the end of the discussion]

Just add water, and that's that! [the matter is finished = that's how easy it is]

Answer 3

The answer that the other person gave on the link you provided is perfectly fine to me. However, perhaps we could extend the meaning of "that's that" to incorporate the context of your example.

That's that - in this case means "Job done/Deal done". It also has connotations of simplicity, implying that something is easily done. E.g. Just put it in the machine and that's that. (or "and job done)

"That's it" also implies simplicity. In your example the last two lines could be: "So that's it?" "That's it." And that would directly mean "We're finished?" "Yes, we're finished".

To summarise, it seems that the meaning in the text you provided is more like "job done/issue resolved", perhaps with an air of surprise: "Oh, that was easy!"