What kind of brass? Every dealer has something they are cheaper on than the others. Ex, Natchez had new LC 223 brass for .11 each, while others were selling it for .20 each or higher. Tell us wht your looking for and we can tell who has the best deal.
I buy my brass at my local gun shop. He caters to us handloaders, as well as to the hunters and trapshooters. His prices are nearly always the best around. If it's not on the shelf, it usually arrives there in a delivery on the next Monday. When he can't get me something in a reasonable time or at a reasonable price, he recommends an online dealer; and usually, his recommendation is among the best deals around.
A dealer like that deserves my business, and I'll go to him first. Keeping folks like that up and running makes sense, so I'm a loyal customer. In addition, I've bought four rifles from him in the past nine months. I need having him around and healthy.