what about cargo? i know they have drastically different spawn conditions but they work basically the same
personally id put them on par with regular chests, while they give less items than a gold/silver chest youre nearly guaranteed to get an item compared to regular chests which are just 3-9 galleons most the time
you also get a chance to get a free treasure chart on top of your free item, and get a super high 1/60 chance of a rare scroll/weapon