"Other things to bear in mind are that in terms of additives, polymeric ashless dispersants counter piston deposits, overbased metallic detergents do not"
Some of these Euro lower SA blends are very appealing as they appear to contain the same or higher quality base oils, minus all the overbased metallic additives/detergents. Mobil 1 Triple may fall into this category now with it's unique additive system.
Lubricants with no or very low ash rely on ashless dispersants for max control of insolubles/deposits.
The price of Amsoil Euro 5w30 is $17.99 qt (PC cost is $13.99) Purely speculating but it's possible this is due to these modern chemistries while still retaining the great solvency/oxidation resistance base oils. It's a known fact that the chemistry required for such blends is more costly. Kind of a best of both worlds approach?