First Strike" map pack were sold "in the first 24 hours" of its February 1 debut on Xbox Live. At $15 a pop, that's $21 million in gross revenue in a single day -- on a single platform!
Notably, Activision Publishing's Eric Hirshberg pointed out that those sales were a "20 percent increase over Modern Warfare 2's 'Stimulus Package DLC'" launch. He added that First Strike, which was also released on PSN and PC in March, "continues to outsell the Stimulus Pack by more than 20 percent."
But hey, let's give our old friend the Stimulus Pack a break -- after all, the poor thing had to suffer the full rage of the internet when it became the very first Call of Duty DLC priced at $15! First Strike had it easy.