Everything has a value. You can't eat a +1 sword.

Fist thing first. When the walls come down two things are important about an item. First, it will help keep you alive. Second, it will work multiple times.

A potion is worth no more than it's effect. Trading it for some service is completely reasonable.

A magic sword is worth all the times it will come in handy during combat. It should only be traded away for something of lasting effect. A lasting safe shelter may be just as treasured.