Thank you so much for your comment and sorry for my late reply. I agree with your point about big networks. In most of the big ad networks -like Google Display Network- you normally know what to expect (in terms of CPI, CPC, CAC) and benchmark data is alrealdy available. Trial-error method is mostly for the smaller/new networks. In other words you can onboard big ad networks with the available benchmark data and use trial-error method to onboard smaller ad networks and compare the metrics all the time. I hope this is helpful.