While it is somewhat strange to hear two "readys" in a row, I believe that most comments on this lesson are missing the intention of già - that lunch came sooner than expected, not that lunch is ready "now". I think it important to recognize the Italian speech patterns here rather than the English. However, in English this phrase might be used more as a question indicating surprise than a statement as Duo created it.
Probably me. Just like I have known myself to say "...ready already?"