ㄴ다구요

'Wait, you're saying…?' echoing back

-ㄴ다구요 is the chatty spelling of -ㄴ다고요, and in most of these lines it repeats what was just said as an incredulous question: 그걸 뭉갠다구요? 'you're trying to lump it all together?' Flat rather than rising, it insists on your own point instead — (1,000원 차이밖에 안 난다구요~) 'I'm telling you, it's only a 1,000-won difference.' The 요 keeps it polite either way.

Register: polite but casual