Castrol Syntec also comes with 10W40. I saw it in my local Wal-mart today and it is abour $18 per 5 qt container.
Speaking of the BMW-Vavoline situation. I made an inquiry to a local BMW dealer asking about the 5W40 oil they use. The reply I got is that now they have a new BMW High Performance Synthetic oil 5W30. It is $3.60 per qt. I am going to take a look at that one to see if it meets the specs MB mentions. I am sure it does.