These are paid for as part of the Squig Herd and so their points cost is part of that unit, just as it is when you upgrade a model to a Standard Bearer or Musician. Killing individual Squig Hoppers or loose Squigs gains no Victory points. However, you will get the Victory points for any remaining Hoppers or loose Squigs if you destroy the Squig Herd they start in, even if the Squigs themselves are still on the rampage.