Its not. They just have 80% market share in a huge market, so they are treated differently. Technically these were optional rebates by intel, which I think is what pisses the intel guys off so much about this.
And rightly so, the whole history of antitrust law is completely full of injustice. It is impossible to tell what is legal or illegal because it is not defined, it is merely a tool for the government control successful companies.
Special discounts: We lower the price if you buy more than X amount.
This: We lower the price if you buy more than X amount, and don't buy from the competition.
