Many people really, in a practical sense, do have to have the Internet, and at reasonably high quality. Work and school being two common cases.
The 'rational actor' model is to economics what spherical cows [1] are to dairy farms. It is a simplifying assumption that is useful for certain general cases, but if you ever find yourself depending upon it in an argument, you're working at too shallow a level.
In this case, though, even if the rational-actor model were valid, you'd be wrong. In the case of monopolies and oligopolies, the rational-actor approach is to, basically, let yourself be screwed by the monopolist.
For example, in my case I'm in an area where I pay more money for worse broadband (ADSL) because I hate monopolists like Comcast. From an economics perspective, I'm an irrational actor, because I'm not optimizing for my own interests.
[1] http://en.wikipedia.org/wiki/Spherical_cow