In 2011, Market Watch had America by Heart sales at 263,000 with the caveat that three major markets were not in its total, including WalMart. Because of that, Market Watch suggested increasing Palin's sales by 1/3. In the end, I think it safe to say that her second book has sold close to 500,000 copies. Going Rogue sold well over 2 million copies and was the number one non-fiction book for 2010. 
As an aside, the Palin/Couric television dual had Sarah winning by an 11% margin on the Tuesday, April 3, she hosted (NBC) opposite Couric on ABC. The next day, without Palin, NBC lost the ratings war for that day to Couric. Finally, comparing Pelosi to Palin, we have these numbers. Pelosi wrote a book back in 2008. Out of 219 reviews of her book on Amazon, she averaged just one star (out of five). The book sold 3,400 copies at last count. And worse yet, at the time her book was on the market (August, 2008), she was serving as the first speaker of the House of Representatives with a popularity rating of 9% for House Democrats.