The point is that if this article is correct about the assumption that AI is capable enough to reduce the friction of consumers rationally comparing options for a far wider basket of goods, then competition will reduce prices. No company wants to reduce prices if they don't have to -- their hand is forced by declining market share (or, with discounters, price reductions are a deliberate strategy to increase market share and absolute profit).

The bull case for AI and consumer welfare is 1) turning more markets into "perfect competition" like airline tickets, and 2) driving actual prices lower because the marginal cost of production is lower with less labor. Even if real inputs don't change, removing labor will reduce marginal cost (which implies that you'll see the largest price declines in labor-intensive industries).