Great point. Revenue reflects the value added of the entire supply chain, not just Apple's. EBITDA/employee instead of revenue/employee would be a more appropriate measure. GP's numbers revised:

  Twitter EBITDA per employee: $211mn / 8k employees = $26k per employee
  
  Google (Alphabet) EBITDA per employee: $93.7bn / 135k employees = $694k per employee
  
  Apple EBITDA per employee: $130.5bn / 154k employees = $847k per employee
  
  Twitter EBITDA per employee if 3k instead of 8k: $211mn / 3k employees = $70k per employee