[user_7832]

Because, in an economic sense, of asymmetry between the parties. You only have a handful of car companies to buy a $30k green 5-door sedan from. But Ford can easily afford to lose you as a customer - Ford is more important to you than you are to them.

An extreme case of this (in some places) is the internet provider. If they know they're the only ones they can basically charge much more than if you were living in an area with healthy competition. What're you gonna do, not use the net?

[xyzzyz]

Ford can easily afford to lose me, individually, but typically things that will cause them to lose me, will also cause them to lose many other customers. In practice, there is no actual asymmetry: if I don’t like Ford, I can just go to dealership next door, and so can millions of other customers, which means Ford needs to be careful.

[user_7832]

Ford needs to be careful, yes. But Comcast in this example doesn't need to be. And for you to compete with Comcast by spinning your own ISP and having your own cables is not likely.

[xyzzyz]

Yes, I agree. My point is just that the asymmetry in market strength is not based purely on the size of the company relative to the consumer. In many competitive fields, it is the providers that are in a precarious situations instead of the customers, even if the providers are large corporations. Consider, for example, McDonalds: it’s a huge company, but it would be ridiculous to suggest that it enjoys significant market power over customers. Many such examples.