The KSC75 are constantly discussed in this forum as arguably the best value for money headphone on the market. I managed to track down a set on ebay, including postage, for about AU$35 Australia (US$27.72), and I'm very happy with the SQ. But in Australia these retail for AU$70 (US$55.44)!!!
They are available from Amazon UK for £9.68 (US$19.01) and from Amazon in the US for $16.54.
I do a bit of international travel with work, but I am yet to see the KSC75 in an airport store - bummer.
I'm really happy with my set for AU$35. At US$20 these truly are a bargain.