I'm surprised people are still amazed at the concept of a high mark-up on electronics products. Pretty much every item in your house that has Made In China has an insane markup on it - hence the reason it's made in china. You pay for the perceived value of that item and the "perceived value" is basically the "benefit / cost" ratio. If you find the benefits received worth the cost paid, then that is your perceived value. Your perceived value can be different than the next person. That creates a supply / demand. The supply / demand ratio is where the manufacturer determines their prices, and that can vary between markets (ie America, Australia, etc).
It's a lot more complex than that, but head phones are far from immune to mark up. If someone makes a device made entirely from cheap plastic called the Wonder Thingie Ma Bob and it cures every ailment in your entire house, and they have the patent on it, then they can charge whatever they want and it's up to you whether or not it's benefits are worth it to you. If no one sees the value in it, then that company will either lower the price (risking a negative market perception by the consumers) or simply redesign it, rerelease it, and price it appropriately with a new name so no one sees the connection to it being the EXACT same thing.
Headphone companies, like most companies, have the benefit of market research and test groups where they can get a general idea of what people will pay for a given perceived value and they can price in that market accordingly.
Of course you economic and business majors out there know it's a LOT more complex than that and there are a ton of variables, but honestly, no one here with a general concept of profit margins should be surprised by mark ups. That's kind of the point of a business. To turn a profit.