securing a revenue stream from the customers before launch

Ouch. That's tough enough when you have a going concern and an existing product - for example, a manufacturer of bespoke machine tools will be lucky to get 10% up front, the rest paid in installments as milestones are hit over the project period (say, 18 mo.). But an established company can often get financing to cover the cash flow.

It would be damn near impossible for a startup with no track record to finance development and manufacture of an unproven product through advanced sales (unless they're very good at marketing to morons).

The fact is that what we're experiencing right now is a top-down disaster. -Paul Krugman