For years, I listened to music through the cheapest headphones I could find. This usually meant those $10 Sony earbuds, the awful plastic ones that leave your ears physically sore and boast of "deep bass" (read: less midrange). But since I was pretty much broke all the time, and rarely bothered to bring my CD player anywhere anyway, the earbuds had to do.
I didn't buy better phones until a few years after I started working with digital audio. While I was at the World Bank's Multimedia Center, the standard for all the video stations was Sony's MDR-7506 (or its original variant, the MDR-V6). The MDRs have been pretty well-known professional units for years--they're staples of mastering and post-production studioes--and lots of people hate them, saying that they're unsubtle and overly bassy. All of which is probably true, but they were miles above anything I'd used before. Suddenly I could hear all kinds of distinct parts in the music that had previously been masked by poor equipment. It was eye-opening, like the first time that I used a condenser mike instead of a dynamic.
Today I own three sets of nice headphones. I have a set of MDR-7506s for work, a Beyerdynamic DT 770 for those increasingly rare times that I do audio editing at home, and some Etymotic earbuds for portable use. I'd say these are reasonably-priced now--only the 770s cost more than $100--but there's no way I'd have seen them as "affordable" during my painful-plastic-earbud years. Which is not to say that I couldn't have saved up for a pair, but it would have been hard to convince me to do so, since I had no exposure to anything better.
Most people, I assume, are basically in the same position. Surely that's the only thing that can explain the proliferation of those awful white earbuds on the Metro. It's a catch-22: the only way people would consider better cans would be if they listened to them, and that probably won't happen until they actually buy a pair, which they won't do because they've never heard good headphones and can't justify the expense.
Some may argue that digital compression makes headphone quality irrelevant, and that could be true in some cases. But at modern bitrates, psychoacoustic compression isn't nearly the sound-muffler that it was during the Napster days. To the extent that it has an impact, compression is way less harmful than a poor speaker setup.
So this is a plea to all those people I see on the train with $10 headphones plugged into a $200 music player (or worse, using the pack-in earbuds). I feel your budgetary pain, guys, I really do. But the next time you feel the urge to upgrade, consider putting the cash into the other end of the headphone cord. I'm pretty sure you'll appreciate it.