> 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…
It could be that they measured a stack of bills sitting on a table, then did the math to make a metal frame to contain $1,000,000. But they didn't account for stacks compressing under the weight of higher stacks, and it wouldn't look as nice if the top part of the cube was empty. Still, it does seem like it would be cheaper to rebuild the case than to add $500k to it. Maybe it's easy for the Fed to acquire more cash…
Based on Fed policy since 2007, they may be happy to hand out cash especially if it's going to be spent.
"Money printer go brrr" and all that...