In some instances you are right !! Many do like the old look but in my opinion, brass is not such a valuable metal ( with the exception of moderate to extremely old pieces or those with historical reference ) that it would hurt to clean it and if the green corrosion eats through the metal,, its worth nothing !! Try to clean the interior of the glass with one of those teflon scrubbies and dish soap. then let it dry !! If the cloudy comes back,, there may not be anything you can do !! There are several things you can try but they rarely work !!
Its fine to give values here if we know what it would be, but sometimes we cannot say with any certainty !! In the condition I see your candleholder in,, about $ 10.00 on a good day !! But this is only my opinion,, see what others have to say !!