I am not sure if this is really a universal test to be honest. For practical goods this of course works. If there is no intrinsic value in a good itself than people don't need it and shouldn't be buying it. But this doesn't hold true for commodities or currencies. Let's say you buy a basket of precious metals including gold and silver, then everybody would agree it's really valuable. For ourselves the intrinsic value would be 0, we can't eat the metals or do something useful with it. The whole value for the commodity basket comes from what other people would pay for it. Same goes for some emerging market currencies that investors buy only with the goal to sell them for more money in the future. The value itself for us 0 because we can't use that money in the shop. As long as other people are accepting the currencies or commodities and exchange them for other goods they are valuable and not a scam, same goes for crypto currencies.