Only 15% of That Burger is Actually Meat

"Water content by weight ranged from 37.7% to 62.4% (mean, 49%). Meat content in the hamburgers ranged from 2.1% to 14.8% (median, 12.1%). The cost per gram of hamburger ranged from $0.02 to $0.16 (median, $0.03) and did not correlate with meat content. Electron microscopy showed relatively preserved skeletal muscle."

http://www.tissuepathology.typepad.com/files/prayson_anndiagpath_dec2008.pdf