True and False.
True that you can get a decent unit for $40-$50… false that any headphone jack one will be “high quality”. With the headphone jack ones, you’re taking an amplifier (the mp3 player) and setting it’s amplified signal to another amplifier (the car cd/radio deck) so you have to kind of “match” the mp3 player’s volume to the car deck’s volume to get good sound. If you want high quality from your mp3 player in your car, get one of the adapters that plugs into the USB of the player. My friend has one for her iPod video that is very near CD quality.
Also, take a look at the Creative mp3 players. I bought a Creative Zen Nano Plus (512mb… but there is a 1gb version), it’s tiny, lasts a long time on a single AAA, and has great sound quality. It can also be used as a removable drive to store anything else on, so instead of using the supplied software I just installed the drivers and drag-and-drop files onto it. I’m assuming this means I can also use it on a mac as well as use it with one of the USB-reading radio transmitter things in my car.