High-End Headphones = Rip Off?

I am starting to wonder if paying bigger and bigger amounts for headphones is worth it.

I bought some Sennheiser HD570 and I was looking at the HD595 because they are one of the highest class of audiophile headphones without an outrages. Then I started looking it the specifications between the HD515, HD555, and HD595. The only difference other then the stamp on it is the range of sound that it is able to produce. The HD515 and HD555 also have a <0.2%>

HD515 – 14Hz-26,000 Hz
HD555 – 15Hz-28,000 Hz
HD595 – 12Hz-32,500 Hz

Now with that in mind let’s look at the hearing of a human. There are sounds that we can hear and can not due to the level of frequency. The sounds that we can not hear are infrasound and ultrasound, infrasound is too low and ultrasound is too high. So what is the frequency range of a human?

Well there have been many studies on it here are the results of three and then we will average out the findings to have a semi accurate account assuming that the research they did is accurate.

Cutnell, John D. and Kenneth W. Johnson
Physics. 4th ed. New York: Wiley, 1998: 466.

They found that the hearing rage was 20-20,000 Hz

"Ear". Microsoft Encarta Encyclopedia. CD-ROM. 2000

States that the level is 15-18,000 Hz

Caldarelli, David D. and Ruth S. Campanella.

Ear. World Book Online Americas Edition. 26 May 2003

State that the level of hearing for a human is in the 20-20,000 Hz range.

So if we average out the three we find that the average lowest frequency is 18 Hz and the highest is 19,333 Hz.

With that in mind lets look back at the at the lowest of the three models its response is 4 Hz lower then human hearing and about 7,000 Hz higher. Thus with their lower model you are getting more then you can hear. So why should you pay more for sounds that you can not hear.

The MSRP for each of the products is

HD515’s $109.95 USD
HD555’s $169.95 USD
HD595’s $289.95 USD

So if the 515’s are already above my hearing then how do they expect me to pay an extra $180 for sounds that I can not hear?

If you know a scientist or a person who works with audio equipment and is well educated that would be able to give me facts about this and lead me in the right direction please let me know.