Most marketers obsess over CAC without understanding its critical flaws. Traditional CAC calculations ignore customer lifetime value timing, attribution complexities, and organic growth effects. I've seen companies make devastating budget decisions based on incomplete CAC data. The real metric you should track? Payback period by channel, segmented by customer quality scores. When we implemented this approach at TechFlow, we discovered our "expensive" content marketing channel actually delivered our highest-value customers with 3x longer retention rates. The key is building attribution models that account for multiple touchpoints and measuring leading indicators of customer success, not just initial acquisition costs.