Then I guess we differ on the idea of what "perfectly targetted" means. You're certainly not going to buy all XYZs, so XYZs vendor would be wasting dollars adve

Then I guess we differ on the idea of what "perfectly targetted" means. You're certainly not going to buy all XYZs, so XYZs vendor would be wasting dollars advertising the XYZs you're not going to buy. So it's not perfect. Perfectly targetted advertising would show you the one XYZ you are going to buy, and stop there.