I would hazard a guess that many of these kinds of companies aren't holding inventory, though. Dollars to donuts says that they're taking that money from the customer, ploughing it back into ads, then using cashflow from future customers to actually order the goods from a dropshipper week or so later.
Some would call it a ponzi scheme, others would call it a kickstarter.
Some would call it a ponzi scheme, others would call it a kickstarter.