The envy-free pricing problem, unit-demand markets and connections with the network pricing problem

A common problem faced in economics is to decide the pricing of products of a company, since poorly chosen prices might lead to low profit. One important model for this is the unit-demand envy-free pricing problem, in which one considers that every consumer buys an item that maximizes his own profit, and the goal is to find a pricing of the items that maximizes the expected profit of the seller. This is a practical and interesting problem which is, unfortunately, not in  APX unless P=NP. We present two new MIP formulations for this problem and experimentally compare them to previous ones from the literature. We describe three models to generate different random instances for general unit-demand auctions, that we designed for the computational experiments. Each model has a nice economic interpretation. Our results show that one of our MIP formulations can sometimes lead to better results than the previous ones from the literature. We also consider a variant of the network pricing problem in which one has to price toll arcs in a highway, and prove that it is as hard to approximate as the envy-free pricing problem.