Ravenol SSL 0w-40

Couldn't help myself and ordered 2 oil changes worth of Ravenol 0w40 LL01 SSL on sale from blaupart. With castrol edge LL01 dropped, I wanted to try the 0w40 as it has the a40, LL01, 229.5 approvals similar to the edge 0w30/0w40 I've been using for my BMWs. Was curious why the 0w40 SSL is more expensive than all the other PAO full synthetics they offer, anyone know the reason?