Reducing the prices on CDs would help, but it would not be likely to make a huge dent in rates of music piracy. There are two major reasons for this.
First of all, reducing CD prices would (of course) not get those prices to be anywhere near what people pay (nothing) when they pirate music. People would still have to pay some amount, most likely fairly substantial) for something that they now can easily get for free. This is not that likely to happen.
Second, buying CDs is not as convenient as downloading music. People are less likely to want to physically go to a store or wait for a CD to be mailed to them when they are used to getting things instantly.
Pirated music is too cheap and too convenient to be effectively combated by lower-price CDs.