That's how much 5 qualified software engineers would cost to employ for a year (gross, including compensation, benefits, payroll taxes, office space, hardware, etc, and that's on the low end of the range). Good luck with that.
So? I've found 1:10 to be a good ratio between leads and grunts. 1:5 if lead is technical and also contributes work and not just leadership/management. And that's when those 10 (or 5) people are working full time.
It costs half a million to employ one software engineer for a year?
Cost per employee is much greater than just their salary.
A software engineer qualified to work on this kind of thing is worth about $350K in combined compensation on the market right now. Typically half of that is base, while the other half is stock and other taxable benefits. The number can be higher. This is the cost of just compensation to the company, excluding the payroll tax. You can, of course, find someone a lot cheaper, but then you'd be a fool to expect the result to be anywhere near as good as what Google can pull off, because if that someone could do what Google can, why would she work for half the compensation instead of applying to Google or FB or whoever pays competitive salaries these days.