What does the に in でしょうに mean?

Question

Recently I was talking to a friend and the topic of credit cards came up. I asked my friend (xx) if they had a credit card:

ところで、xxはクレジットカードを持ってる？

and got the following response:

そりゃあ持っているでしょうに。

I'm not too sure what the に at the end means, but searching around the internet it seems to be related to のに. However, sentences that end with のに typically indicate disappointment/regret etc and I don't believe that was the case here. I found this:

あなた、それくらい分かっているでしょうに。 You know that, don't you? この場合の、don't you? に相当するのが、「でしょうに」です。

which seems close in meaning, but it doesn't feel like it's from のに. Any elucidation on this would be helpful.

Answer 1

「そりゃあ持{も}っているでしょうに。」

For the majority of native speakers, this is not a regular, "calm/relaxed" way to say:

"(Yes,) I have (a) credit card(s)."

That is why I asked above how exactly you asked your question that triggered the use of the highly nuanced and possibly emotional に-ending.

My first impression when I read this question before the edit was that the speaker was slightly irritated or surprised at your question -- "Of course, I have a credit card. Why would you even ask?". That could happen because credit cards are far more common in Japan than what the popular J-vloggers on YouTube seem to want you to believe.

According to goo辞書, 「（よ）うに」 does the following:

★後悔・不満・非難・疑問・感動などを表わす。

That means "expressing regret, dissatisfaction, criticism, doubt, emotion, etc" and this is precisely why I said what I said at the beginning. Your friend's reply is clearly nuanced. A regular, non-nuanced reply would have been along the lines of:

「（ええ、）持ってますよ。」

The difference between that and the actual reply you received is huge.

What one could still not tell is exactly why s/he replied that way. To analyze it, we might need to read the entire conversation that took place, which I will not ask you to show us. As a native speaker, I could just almost hear the silent 「なんでそんな（当たり前の）こと聞くの？」.