> For all we know, the middle is just air and crumpled-up old newspaper. I think this is the answer. I suspect the exhibit designers had a cool idea for a display, did a rough estimate of the area needed and then commissioned the exhibit builders to make the big metal-framed cube. Either they made an error in their calculation or the innate variability in the size of stacks of used bills threw it off. It's also possi…
But who says that they didn't actually request $1.5M in used bills after doing the math of what it would take to make a cube. Or fill it up with $1M in used bills, and come back and make another request for $500k that also got approved...