"Do you have expensive things?"
Translation:Masz drogie rzeczy?
Why the different adjective when using ty vs wy? Is there a difference due to the use of czy? Czy macie kosztowne rzeczy? vs. Masc droga rzeczy?
It's not because of ty/wy, it's not because of 'czy', it's because of the noun phrase the adjective is a part of.
If the noun phrase here is "expensive things", and things are definitely plural (not masculine-personal plural), the adjective for "expensive" has to match and therefore it's "drogie".
If you had only one "thing", which is feminine even if it looks masculine, it's "droga rzecz".
If instead of "things" there was a car, which is masculine, then it would be "drogi samochód".
The adjective can depend on the person when it's describing people. Compare "X is/are nice":
If X is masculine, it's "miły", if feminine, it's "miła", if neuter, it's "miłe".
If X is a group of people with at least one man (masculine personal) it's "mili", if it's anything else, it's "miłe".
So there would be a difference between ty and wy - if the adjective described ty or wy, but it does not here.
I think my question had to do with the use of kosztowne in one example and the use of droga in the other. I wondered if one were more formal than the other. Thank you for your quick and informative answer!