Before we all get lost in the financial minutiae, lets remember what those retained on PAS are really there for. Their experience and Above Average nature (this year may be different but all previous boards have required the same criteria as for promotion) make them an essential part of the supervisory chain of any current Sqn with limited experience elsewhere.
I recently witnessed a combination of Flt Cdr and SEngO willing to sign of a inexperienced crew to fly an ac with a fairly major fault. It was only the PAS guy who overheard this that stepped in and explained how and why what they were proposing may lead to the major damage to the ac or potentially worse and stopped the whole debacle.
In any other sensible world of employment, they don't get hung up on rank, purely on value to the company and cost to keep, a bit like our medical brethren. The cost to train from new is several million so, in perspective, it's a pittance to pay for an experienced and proven operator adding to our DH's assurances ( which is what life seems to have become all about). As has been said already, the days of the crusty old wee-smelling PA sat in the corner adding nothing are gone.