530d vs 730d running costs?

[RicoOS]

I've already asked about a potential purchase of an F11 530d touring and thanks for the very useful response to everyone who answered. But as a secondary question, what are the likely maintenance cost differences between an F11 530d touring and a F01 730d?

Would be done by a specialist and would be doing the same likely miles so circa 20-25kpa, both starting circa 2010 plate and probably already with 100k on the clock, with full history.

Part of me has a hankering for that super luxury and I'm just trying to understand the likely maintenance cost difference, given the same engine etc?