Just like most bicycle parts, chains have a pretty wide price range. What are the factors weighting in on the price of a chain ? (Other than width/bike-compatibility characteristics)
Material: The material of which the chain is made of affects the price greatly. Titanium chains, while not common, are ridiculous in terms of price. Often, in terms of material, it is the 'finish' of the chain that can affect its (claimed) performance and thus its price. For example a DA 7700 chain is nickel plated, DA 7800 has a zinc alloy etc etc. These are claimed to increase life span and reduce corrosion
Weight: As posted above, the less you get, the more you pay.
Technology: Hollow pins, unidirectional chains that improve chain pickup etc. can increase the price of a chain as well.
Lastly. Name. Campagnolo is still silly expensive for being a chain that is no better than that (arguable, I know) of comparable brands.
I'm guessing, just like every other component on a bike, the two factors are durability and weight. Basically, a titanium chain will be a lot lighter and stronger than a steel one, but at a higher price.
And just like every other component, you should consider how much do you care about shaving a few grams off your bike vs the price, and how much of a beating you expect it to take.