Comment by flokie

The challenge with that approach is the variation in both (a) queries and (b) other players. (a) There are a small % of queries that are knowable for you to target on exact, or you are required to update and prune infinitely over time. [https://twitter.com/Google/status/1493681643290300425?lang=e...]. (b) A mix is better than a fixed CPA at a set price, up to to the player to pick the acceptable range. At a fixed price and many players competing for the same 100 10$ conversions, the price would quickly rise for those same conversions anyways. You're replicating the work the computer is doing, but doing so with the illusion of control.