When you send Brownells a copy of you C&R, you get special pricing on their web site. If you just go to their site and look at, say a 20 round A-15 mag, it will show you one price. After they get you in their system, you log on their site, look at he same AR-15 magazine, and you will see the "general public" price and "your price"
Make sure you sign the copy of your C&R in blue ink. Retailers want an original C&R and signing it in blue ink means that it hasn't been dupplicated on a copier.
That $30.00 you paid for your C&R will pay for itself many times over.