To aid in answering your questions David.
The main reason for difference in pricing (IF IT WAS SAME SERVICE, SAME FLUIDS, SAME RIP OFF'S, SAME CHECKS AND SAME REPLACEMENTS OF PARTS) Is mainly due to Lexus service Centres although owned by Lexus Australia, are independently run. so there is not a set price for guide for servicing.
For example.
Smiths Chips are owned by Smiths, but supermarkets can sell them at what ever price they want.
Lexus of chatswood is owned by Lexus, but service centres can sell thier service at what ever price they want.