Thanks for the notification. And of course it is not a typo and it is included in the incubator. Was this by any chance on a Strengthen skills exercise? There have been other such glitches there. Since this is an issue to do with the Duobot and is out of our hands could you please post directly to Duolingo Help.
That would be appreciated and would help resolve this issue.
Thank you to both of you for the reply. That makes sense. However, if you allow me to say- the difference in pronunciation between φτηνή and φθηνή is not really discernible (or only almost barely so). Besides that, I distinctly remember listening to the sentence at the slower speed (because I knew both words were valid), and it sounded more like φθηνή than φτηνή to me (but again, these particular words, especially when said by a computer voice, are hard to distinguish at any speed...).
In my experience, if the sentence discussion page has the Greek at the top and the English at the bottom, and the student was asked to type in Greek, it can only be a listening exercise.
If they have to type in Greek and the Greek is at the bottom and the English text is in big, then it's a translation exercise.