Not really because you're paying for the roll of the dice not to get the actual desired image. So it's more like the minimum it would cost is 6c with no celling.
Of course it is, but it's not an either-or expense it's both-and. For most projects you need to do a lot of trial and error to get the right image, so it's the cost of someone who knows how to do that trial and error effectively + probably a few hundred generations per hour.
If a human being is making that determination, their time is probably worth more than the 6 cents it cost to generate the image.