Filters you can defo get cheaper for good quality non OEM. I personally like to use AC Delco filters (available at Holden dealers if you absolutely can't get them anywhere else) but you can't get a fuel filter in this brand so I usually use Ryco. Check SCA for prices and buy from them (shop on line, parts get free delivery from SCA I'm pretty sure). The pollen filter is a gauze screen, take it out and clean it, no need to replace it unless it's fucked and even then you can run without it if you really want to.
Oils, get them from your favorite auto store. Go onto your favorite oil website and use their oil selector to pick which oil you need to use and but it then do it yourself. The rear diff is a PITA because the cover needs to come off the drain it but apart from that it's an easy enough job.
The rear suspension arm bushes I'd bet are dealer prices. I just today priced a rear UCA ball joint as mine has started to make a bit of noise following a camping trip across the Nullarbor - Balljoint $503, complete rear UCA (arm, bushes and BJ) $1826. That is parts only.
I can see the rad or hoses being a RWC item if it's leaking badly and dropping crap all over the road but a coolant flush is not a RWC item - tell him he's dreaming