...known as secondary-line price discrimination.1 The Clayton Act does not prevent price discrimination "on account of differences in the grade, quality or...commodity sold, or that makes only due allowance for differences in the cost of selling or transportation, or discrimination in 538 Antitrust: Efficiency...

...line of reasoning is that it takes no account of the'provisos of the section. If the discrimination is "on account of differences in the grade, quality, or quantity of the commodity sold ", or makes " only due allowance for difference in the cost of selling or transportation ", or is " made...