Downloadable content for Xbox 360 and PS3 games may prove to be a constant drain on our pockets every few months, but it looks set to continue for the Call of Duty franchise for a long time to come.

Gamasutra is reporting that Activision has netted $70 million from the sales of Call of Duty: World At War map packs since mid-August. With each map pack costing $10 each that means that a whopping 7 million gamers have downloaded the content.

The results come as part of Gamasutra's in-depth analysis of U.S. console retail sales, which concludes that Activision has netted "$45 million in revenue on top of retail sales of Call of Duty: World at War on just the Xbox 360 and PlayStation 3."

With the release of Modern Warfare 2 just around the corner it goes without saying that Infinity Ward will be busily working on a host of new map packs to encourage us to part with our money. And as long as they're good, we don't mind too much.