Low single digit could easily be viewed as significant. Given this scenario, it would be easy to guess google wasn't basing their decision entirely off cost. You'd have no real idea in either case unless you were involved in the decision making.
My wild guess is processing costs. With the amount of traffic they see, encrypting every page of every item someone looks at could potentially be very costly.
We all know what's said about correlation and causation.
Of course, it applies on the flip side of the argument as well.
My experience (including pharmahuasca, smoked dmt and 5meo-dmt, and so much more) is hallucinogens just hold up a magnifying glass to what's already there.