The first problem with your hypothesis is that OnePlus isn't some little startup in a garage, but a sorta adjunct of Oppo. Now some whiny people howled about how they were "lied to" when they discovered that connection (they're idiots), but that should be reassuring since they aren't exactly going to fold if a customer's check bounces.
The next problem is that there isn't an instant correlation between units sold and money ka-chinging into the bank account. This isn't like running a restaurant where you can buy tomorrow's ingredients with tonight's receipts. As the item I linked above explains, it takes them three months to get their screens. Let's pretend they have to sell their initial run before they can order more screens. By the time they have the cash, it's next month, then they get their screens and they have the next batch ready to sell. In November. When the iPhone 6 with a proper-sized screen is out along with the Nexus 6 with the Galaxy S6 lurking a few months beyond. They'd be dead - as would any business - which is why there are credit lines and standard remittance timelines.