Considering a CD takes 2secs to press ( including cooling ), and the ´master-copy´ looses detail on every press ( can take 2-10K of cycles ), your lucky if you get one of the first ones off the press, as the rest will decrease in quality. Buy two of the same CD, play them, chances are good that they will differ in quality.
Serious press-companies runs with a new master in very short cycles. Getting better quality sounding CD´s.
The first one off the press sounds just astonishing!
Also, I just get scared when knowing that a lot of studios plays with a simple transistor-/household-/megaboom-stereo
for reference/mixdown-reference. Because they know that there´s were the music will be played the most. They make it sound good on those thus they know that will sell them more records. Ugly, but true.
Thanks