All the analysis, predictions, recommendations and actions your campaign management system will take should be within boundaries.
In most of the social media channels, campaigns are at the top of the hierarchy, where the most critical attribute is budget. In your ads objects hierarchy, it is a step higher from the campaign level.
Call it contract, goals, initiative, IOs, or just boundaries. This is the level where you set the expectations for your cross-channel campaigns.
This is the most important meta level, specific to your system, where all the results will be measured against with.
Let’s say your CLTV (customer lifetime value) is $500. And your expected CM (contribution margin) per customer is $300. This means you can afford up to a CAC (customer acquisition cost) of $200 (without considering any other variable cost.)
You can take these numbers as boundaries (or targets, or goals.) Then you can compare your campaigns’ performance on each channel.
Moreover, if you already have CR (conversion rate) numbers for your funnel, you can set target costs at different steps, i.e., your CPC (cost per click) shouldn’t be higher than $1 if it takes you 200 clicks to get a paid customer.