They do have this, you can choose to bid for a target conversion cost (I want to pay at most $x per conversion). In general I find all of this pretty silly as a Google employee.. I don't think you can distill the complexity of any change down to one article. Say for example that Google did just raise how much advertisers paid per click across the board, why would that lead to billions of dollars in profit? I would bet that the majority of advertisers on Google already spend their whole budget, so that would mean that now they would just be getting less clicks and conversions per dollar of budget spend. Logically they would then move some of this budget to other advertising channels such as Facebook. Charging more per impression always has second order effects, but who cares about that on hackernews