Here's proof the price of electronics is going down. I was transferring
files to a new computer, and I came across a .pdf from the October 1985
kitplanes magazine with the title "The $10 Airplane Headphone, Kodak and
the Shack are back to save Your Ears and Wallet." Written by Jim Weir of
Radio Systems Technology in Grass Valley, CA. (I've met him!) The
modification adds a transformer to the speaker line to match the
impedance of a cheap headphone to that of aircraft systems.
Now 23 years later that same headphone modification in the November,
2008 Kitplanes magazine and costs only one dollar.
Unfortunately, the quality has suffered a bit. The new version just puts
shrink sleeve around the transformer while the 1985 version used a 35mm
film canister to hold it. Those are getting scarce these days.