Media Advertising Discounts?

[Reuben82]

I was just confronted by a company that managed advertisements such as PPC programs, etc...
Their website had the following proposition:

Due to the volume of business we deliver to our online advertising and marketing suppliers, we have buying power and price discretion for many of the sites we work with. The result is that we offer online advertising rates that are at least as competitive as if you were to contact them directly and in many cases even better!

Does this sound legitimate? I have never heard of anybody getting a "Discount" unless they had a private relationship? Does anybody know any larger websites or companies which would support discounts at Quantity Buying?

[JohnKelly]

Standard agency discount is 15%, they could pass a portion of that on to their own clients.