CD Clubs -Press their own CD's?

I was thinking of joining a CD Club, like BMG or Columbia House, and I read the following quote from Dealdude.com, "The clubs press their own CDs, tack on shipping and handling fees of about $2 per CD, and work out special royalty deals with the labels...".

What is meant by, "The clubs press their own CDs"? Are these inferior to what can be purchased at the store?

http://dealdude.com/cdclubs.html?source=findwhat