The cost of switching matters (and is talked about in the article as well). If there is a significant cost, then that means less competition, and it makes it hard to categorize them as the same market. Compare the friction of switching between a Samsung TV and a Sony one, vs the friction of switching between an iPhone and an Android. Most people wouldn't mind the former, but would mind the latter

I can only assume they mean Apple will send you and your family to a gulag if they catch you leaving or your neighbors says you don’t have a picture of Steve over your mantle. Otherwise if that is not what literally is happening, that comment is really trivializing the tragedy of what happened to millions.

If an iPhone owner wants to use an app that Apple has banned from the App Store, they cannot simply purchase it. Instead they must make the widely disproportionate move of spending many hundreds of dollars on an android phone. In practice almost no one will switch phones just for a single app.

Similarly, a resident of a communist country could theoretically leave and buy things elsewhere, but in practice almost no one will because of the high overhead of moving countries.

“Using an iPhone is basically like the Gulag” - HackerNews