The Kindle Fire is Amazon.com's best-selling product, the company said in its first-quarter-earnings release. And it's being treated that way by the Amazon ad sales team.

Amazon is pitching ads on the device's welcome screen, according to an executive at an agency that Amazon has pitched. The company has been telling ad agency execs that they must spend about $600,000 for any package that includes such an ad.

The ad campaigns would run for two months and also include inventory from Amazon's "Special Offers" product. For $1 million, advertisers would get more ad inventory and be included in Amazon's public-relations push, according to this executive and an exec at another ad agency."