Why do some music CD's have a hole punched through the plastic case?

Answer 1

when there is a hole punched through, its usually through the bar-code so that way they can be designated as promo cd's (promo cd's are given to music stores, radio stations, etc for them to play) the hole is drilled so that they cant be returned for store credit or cash refund at music stores.

Answer 2

This indicates they are sold at a reduced price. They may be promotional copies, or Cd's that didn't sell as expected.

Answer 3

The record companies are longer producing these and will not stock them anymore they also reduce the price for a quick sale, they did this with LPs as well.