Playing around with
the Cobb calculator, where costs are calculated in victory points as well as armor units, a superheavy without AP guns costs 12.56 VP, rounded down to 2 AU. Add the antipersonnel, and cost increases to 14.23 VP, which rounds up to 2.5 AU. So I'm fine with either of these values when playing a scenario from the book.
I never use the tread damage for superheavies, so I'll trust the conventional wisdom that tread damage brings it up to 3 AU.