i'd imagine when the first headphones came out (some still are), they were fairly expensive. and are now down to the point where they are given away, granted those can hardly count as an actual reproducer of audio... i wonder if someday we will be asked by the flight attendants on our way to mars if we would like to watch "matrix 84, We Were Serious When We Said It Was a Looping Program" on our way to mars and be given a set of retina projectors to do so...