If an ISP hosts content, would analysts also say that they "have no bandwidth bill"?
Yes, they very well might. The ISPs costs are largely fixed, it doesn't really cost them much to stream you a movie or whatever.
Everything costs nothing while you're using resources that you've already paid for, is a more accurate way of looking at it. At the point you exhaust those resources, the cost is the cost of adding more.
It's like the old memory/cpu/whatever is cheap argument. Yes it is, until you run out. Then you're in trouble.
This article states that "[Google] has purchased unused fiber optic cable known as 'dark fiber'. ... Its costs for bandwidth are then amortized across the life of its fiber and routers." Sounds logical to me -- it doesn't seem like Google is "getting away" with anything here.