500 copies cost the same as 1000 copies. Its because most manufactures don't want to make a glass master for anything less than 1,000. With that being said, you can press as many copies as you want, you just pay more per unit. And depending on the manufacturer, you could get 100 pressed, they just recommend you get more. I think also some manufacturers will press 1,000 regardless and throw away the excess copies, I'm pretty sure discmakers does this.