Comment by naijaboiler

Exactly pricing discrimination (i.e. selling at different prices to different customers) is absolutely legal and is market efficient in a market with multiple sellers and multiple buyers.

Pricing discrimination combined with monopsony(single large buyer) or monopoly ( single large seller) powers is not market efficient. It leads to higher prices by end consumers. Price discrimination via collusion + Walmarts monopsony in grocery industry violates that 1930s act and is illegal