Suppose there's an economy where everyone is spending 80% of their energy building refrigerators. All day that's what people are doing. Nobody actually needs these refrigerators, so they just keep building them and stacking them up in the corner.
Then one day an intrepid young entrepreneur decides "hey, this whole refrigerator building thing is kind of silly. It's kind of a waste of resources. I think I'll start betting against refrigerator companies." Then he takes a whole bunch of money (that's not currently tied up in building refrigerators of course) and short sells the stocks of companies that make refrigerators. This causes their stock price to go down a bit (or rather, to go up more slowly) which drives money out of refrigerator building and into other things, like making televisions or something.
A year or two pass and suddenly everyone has an epiphany. All these refrigerators everyone has been building and stacking neatly in the corner aren't actually worth $2000 apiece. In fact, since there's so damn many of them, they're only worth like $3.50! the economy crashes! all the refrigerator companies go out of business! all the investors in refrigerator companies lose their shirts! people are committing suicide left and right because their refrigerator stockpiles are suddenly worth nothing!
But our intrepid entrepreneur is doing quite well. You see, all that money he drove into making televisions was safe because the value of televisions was not inflated. TV's were actually worth $1000 apiece, and there was no oversupply of TVs so their price stayed at $1000.
So what was the value of the entrepreneur's work? well, he kept a whole bunch of energy from being expended on building stockpiles of refrigerators. He didn't himself go out and build televisions or anything. No, his labor was more abstract and more intellectual, but still quite valuable.
Resource allocation is everything.