Impact: One factor we would chalk this up to is the power of spending money on marketing. The marketing campaign for the first title was about $10 million, while Valve claimed they were spending $25 million on Left 4 Dead 2. This was clearly a factor in driving sales as the title was also forced to compete with the massive launch of Call of Duty: Modern Warfare 2. This was another November sign that for the right product the market is still hotter than ever.