I wouldn't call 20 bucks for 2 batteries + a charger expensive....
They aren't AA batteries.
He's talking about the single Epic 4g Touch battery: http://www.amazon.com/Samsung-Epic-Touch-Standard-Battery/dp/B005LPETVK/
$18.90 ain't too cheap but worth it when you keep worrying about battery life. I went with the Anker batteries (2 are included) so my sister could have one but I'm wondering if the official Samsung 1800mah model is better quality.