Not a bad price (relatively speaking) for this engine oil.
Shell Helix Ultra X uses unique PurePlus Technology base oils made from natural gas to help high-performance engines operate at maximum efficiency by helping to protect them from power-robbing deposits and wear. It helps to reduce engine friction to provide enhanced fuel economy.
A3/B5, BMW longlife, seems similar to Castrol at $46 from Supercheap, unless people like Shell, and often these things are prefferences and brand loyalty, which is OK for $6.