You'd be forgiven if you think that's a stack of cash. Actually it's a realistic wooden sculpture called "Lunch Money" by Randall Rosenthal. His art exhibition seems like a lot of fun:
Carving a piece of wood into a bunch of newspapers, or books is hard enough, but using trompe l’oeil painting techniques, Randall Rosenthal manages to make his works look just like the real thing. Trying to keep his audience guessing, he normally just allows just one of his sculptures to be touched, while leaving them to discover if the rest are also made of wood.
His “Lunch Money” sculpture, representing stacks of hundred dollar bills in a corrugated cardboard box took six weeks to carve and another six to finish painting. To get their hands on that kind of wooden cash, art lovers had to pay $25,000, the real kind.
Oddity Central has more: Link | Randall's official website
Similar concept, and one of my favorite art pieces in Washington, DC, is Ghost Clock by Wendell Castle at the Renwick Gallery.
http://americanart.si.edu/collections/search/artwork/?id=31977
http://www.randallrosenthal.com/Pages/New%20Pages/card_box_page.htm