That only works if the Tesla don't bother to deliver the 1,000 'Founder' Roadsters, or Tesla have a way of making them for free.
In two years they'll have a new thing to take deposits on. Stack the pre-orders, roll to the next announcement, deliver the last thing, then do it all over again. They're floating a lot of cheap financing this way.
In the meantime, the approach of announcements & pre-orders keeps their stock charged, which they can also abuse for financing if necessary.
It's precarious and dangerous (inevitably stock market decline & recession), and it works extremely well while it works.
More generally, my point was that producing a high-end vehicle with (most likely) much better margins for the company than, say, the Model X, would subsidize advancements in their more accessible options.