Now, MD is being pitched as a supremely flexible digital home recording medium, and sales are taking off. You can move or delete individual tracks, or erase the entire disc. MDs can be reused, and recording is simpler than using a cassette deck. MDs offer fidelity that is shockingly close to CD, though on the warm and fuzzy side. Previous incarnations of MD were decidedly not ready for prime time.
Recordable CDs are the most recent gee-whiz development.
But if you make a mistake during the burning process with CD-Rs, you must toss the disc or live with it. CD-RW discs are substantially more expensive. The difference between data and audio grades is all but imperceptible. Some of this cost is new technology. But a bunch of it is also a tax arranged by the recording industry that builds in payments lost to artists because of home taping.