Lower prices in more competitive markets are usually a short term phenomenon as players fight for share and sacrifice profits (see retail). Over time, the weaker competitors die following that strategy.
Beer market is a good example, as is the soft drink market. Craft brewers or local drinks cannot compete at all without making huge investments to expand markets and get shelf space. By selling to a major company, they gain access to other markets and consumers benefit by expanding their options. Otherwise, Goose would remain a niche brand in Chicago, and you wouldn't get it in Buffalo or LA. Again, tell me how the consumer doesn't benefit from having their $15 case of Bud or $10 six pack of Goose nationwide?
Consumers benefit not just from cheapest prices, but from having a wider variety of choices, and a higher probability that the product will be available to buy for a long time.