From HP's point of view of not given them a penny for maybe 20 years - and now I'm paying them $2 a month. They can knock off the cost of making and sending me a new cart - but they're ahead from this. A transaction has occurred due to this innovation and both sides are 'happy'. Innovation/Capitalism - should be catnip to this audience.

I agree that I can't predict the costs exactly - but ballpark is good enough. Like cutting the cord. You don't know how your cable price might change, Netflix prices might increase, your provider might shift cost to your broadband to compensate - but for now it works out and presuming nothing major changes, you'll be fine with incremental stuff and maybe make another bold decision in a few years.