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?"
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?