PS I asked a Americus Records and they said it will be about $3000-3500 to make 1000 CDs. It seem a bit too expensive and too many CDs.
I've looked into this before myself.
Basically, the overhead costs of making the glass master, designing the packaging, etc. account for a lot of the initial expense. So the smaller the batch of CDs, the higher the price per disk to manufacture. But you reach a point where you're pretty much are just paying for the additional disks themselves (and associated packaging and shipping, etc.).
So a run of 300 disks might cost $2400 and a batch of 1,000 of the same disks might only run $3000.
Bottom line: it's hard to get a deal on a really small batch of CDs.