"Unreasonably" is the key word there. What is unreasonable? I think that for the vast majority of subscribers, they get FAR more than $10/month in value (or whatever it costs). Cable costs something like $100/month and it's arguably far worse of a product. Is $50/month for Netflix unreasonable? For some I suppose, but for most I'd be willing to bet no. Remember Ballmer saying no one would pay $500 for a phone? :)
And he is right. A smartphone is more than a phone. How can Netflix be more than a video player? One way seems to be to become a producer.
Back to Spotify: How to be more than a music player?
Roku is the opposite side of the same strategy: everyone keeps buying them even though their interfaces and app ports are generally less polished, the hardware often less capable, than much of the competition. It's offset by being simple and well-understood (ever see someone try to use that Apple TV remote touchpad for the first time?) and by running pretty much every TV/streaming app out there.
You and your wife both know (subconsciously at least) that people will switch to HBO, Hulu, or any other number of services if Netflix gets unreasonably expensive. It's broke college students that buy Netflix the most, and they would have to get rid of their biggest set of subscribers to raise prices significantly.