Slitherine

I want to build a preceptor house in Media which needs papyrus. Looking at Babylonia with Papyrus, it has a trade range of 5. Looking at the jpeg, we can see that Media is within the trade range of Babylonia and should be able to receive papyrus as a trade good.

Now here is a screenshot showing Media with the preceptor house in the building slot. Note that it shows Papyrus as Trading Required but then does not show Babylonia as a region within trading range for Papyrus. It also shows a negative monetary cost for the preceptor house. Is this a bug or am I misunderstanding how trade range works?

The trade range of the importing region is what matters, not the trade range of the exporting region. Since Media has a trade range of only 3, it's too far away to import goods from Babylon.