Germ they aren't cheap, luckily I had two Moultries to exchange that both quit working after a week of use and a gift card. The unit sells for $599.99 and the Reconyx RC55 which is the same camera but with a standard IR flash instead of the covert IR flash which is $549.99 Its not a cheap unit but it will make up over time with battery costs.
www.chasingame.com did a review and was able to capture over 28,600 photos on a set of Energizer batteries and the camera was still reading 6% battery life.
MathewsShooter The tree is angled down and the sensor is designed to actually to pic up movement lower to the ground. It should work just fine.