They could give them out for free.
TV companies (Cable/Sky) have 2 main revenue sources advertising between TV programmes and the subscription charges for consumers to use their services. Generally in the UK the TV boxes (like Virgin's Tivo or Sky Plus) are free when you subscriber but you have a minimum contract, say a year, before you can change.
Now sure what you get isn't quite the same as TV companies, there aren't adverts between playing games however, if Sony, MS or Nintendo ever moved to a fully subscription model, you'd theoretically get the consoles for nothing but you'd pay more for the subscriptions.
So instead of £40 a year for PS+ only then £300 for the console once, you'd pay say £20 a month for 2 years PS+ and the console. For the consumer, you pay only £20 upfront so better for those who have trouble saving but in the end the cost to Sony is £480 instead of £380 over the 2 years. Although, I don't think their infrastructure is set up the same as Virgin or Sky, they don't have people in shopping centre's trying to flog you the subscriptions.
... this what you mean?
Hmm, pie.
