History: What is a performance feature of subtractive synthesis?

What is a performance feature of subtractive synthesis?

• Subtractive synthesis is often more expensive than additive synthesis for a computer to calculate.
  The opposite is true.
• Subtractive synthesis is often cheaper than additive synthesis for a computer to calculate.
  Correct!
• Subtractive synthesis requires no calculation.
  This just isn't true of anything on a computer.
• Subtractive synthesis is often about the same than additive synthesis for a computer to calculate.
  There is a difference...