What makes an expensive speaker expensive

To quote from Wiki:

"Adam Smith recognized that commodities may have an exchange-value but may satisfy no use-value, such as diamonds, while a commodity with a very high use-value may have a very low exchange-value, such as water."

But if Magico, et al, started marketing a speaker "under 15 grand", it would be labeled as "entry-level" and thus raise the price of the other products. @emailists is right insofar as the R&D and production put into these high-end products, much like a McLaren car or a Patek Phillipe watch - they are technically advantageous and, when paired with the right equipment, gorgeous sounding.

But for every TAD, Wilson. Magico, and other six-figure speaker, there are 3- and 4-figure speakers that satisfy the listener to the same extent.   

But for every TAD, Wilson. Magico, and other six-figure speaker, there are 3- and 4-figure speakers that satisfy the listener to the same extent.

until they experience TAD, Wilson, Magico ...

Money make an expensive speaker more expensive. 

Quality of drivers,crossover and cabinet as well as were it is made and markup.

The difference between a very good expensive speaker versus a very good inexpensive speaker is usually size and ability to go full range in larger rooms.