It doesn't seem like that 50% number would just keep scaling with salary. There is a cap on payroll tax [1], administration stuff around administering health, vacation, etc. doesn't change that much, office space.. maybe so with things like the Apple spaceship ($5 billion with capabilities for 12,000 employees; amortized over 25 years would be $16,000 per employee so I wouldn't think so).
[1] https://en.wikipedia.org/wiki/Payroll_tax#/media/File:Effect...