[JangoSteve]

The most obvious difference between the mentioned markets is consumables versus one-time-ever purchases.

With consumables (which includes things like cereal), you decide which brand to purchase, and you use or consume it. Then, the next time you need it, you must decide again which to buy and have virtually no downside to purchasing a different brand (no lock-in from the previous purchase).

With one-time-ever purchases (which I think includes subscriptions or recurring purchases where there is a barrier to switching, including games where you have saved progress through levels and rack up points or a high-score), you decide once and then stick with it. I think that's where competition can easily pivot from healthy for a business to merciless.

Then there are things like airline seats which are technically commodities, but not entirely. With airline seats, there are barriers to information (such as being able to use e.g. Kayak to compare prices, but having Spirit excluded from Kayak within the US means you must know to also check Spirit's site), and there are MVP and rewards programs and airline miles, etc, and there is also quality and ammenities, and the fact that you never know how much a ticket with luggage and a snack is going to cost until you go through the entire checkout process (and who has time to do that for all options). So, airline seats seem like they should be commodities, but they really aren't.