Sales, marketing, accounting, legal, and financial controllership are going to skyrocket when this company has a revenue stream that is worth NPV=$19B.
This is a credit to the company; who like instagram was able to build much value with few FTE's. But building a company "worth money" and building a company "making money" are really different things.
This is smart from a founder's perspective, because in a sense all of those other employees would just be dilutive of attention and likely equity. But from an economic perspective, it's jumping the gun a bit to conclude what the steady state economics will be.
Assuming Google/Apple maintain respective strangleholds, continue to share the wealth, etc. The "app store" craze could fizzle out, nobody knows for sure.
So that's a revenue that, today, is probably a sizeable fraction of $400m/year. All that with a few dozen employees.