Marketing Metrics Every CMO Should Track
- The number of leads from each channel
- The revenue from each lead
- The cost of the channel
This gives you both the cost of each lead (3/1) as well as the return on each channel [(1*2)-3]. Compare them, and find out which channels are your most efficient. If there is a lot of difference between your best and your worst performing channels, consider killing the latter and using the budget on the former.
(Of course, there are better and more sophisticated ways of calculating ROI, and if you're doing that already, good for you!)
This is all very basic, and most CMOs would be aware of this already. If you're not, start now.