The price is right!
Or why things mean different things to different people
If you look at the picture and think that some people have made a mistake, you are correct. An adult cassowary is one of the most dangerous bird in the world. It is considered more deadly than ostriches and emus which are bigger. That modern man is farming ostriches and emu and skipped the first domesticated animal tells you a fair bit about cassowary.
There was one saving grace. If a young bird is raised by humans, it will usually imprint on the humans. Imprinting does not mean that the human is safe from the bird. It just means that the bird thinks that it is similar to a human.
Now for the fact. You could trade a cassowary for a woman in certain civilization (Full Disclosure: It is anecdotal as the civilization did not record the price list in writing.). Now, the question was who benefited from the trade. The cassowary hunter had to steal an egg (or a chick) from a nest risking life and limb. Once the cassowary was bigger, he also had to risk the bird not turning on him. So it would seem that person getting the wife would benefit. It was not that the people lack things to trade. They had pigs. Apparently eight pigs was worth one cassowary.
There is reason to believe that the cassowary was viewed as a luxury item. Its meat was seen as a delicacy and its feathers were prized possessions. Certain people viewed the bird as kin. Others used it for ceremonial sacrifice. The bird was an expensive meal, an expensive fashion accessory or a communal event. Or possibly all of the above.
Now, I am not interested in justifying if a wife (I doubt the woman was a slave) is worth a cassowary. I am sure that there are some husbands who consider a cassowary the safer option. The point is that the owner of the cassowary only had short term benefits. You could pluck the feathers periodically (with some risk) but you could only kill the bird once.
18,000 years ago, some people thought that buying a cassowary was worth the price.
For more facts on Cassowary and the people who had a linked to them, please read this article by a fellow Medium writer.