are expensive oils worth their money

Talking to one of our senior members of our club about servicing of vehicles.He has a 1995 diesel GQ patrol with turbo has done 580,000k's kept in immaculate cond. he only uses it to tow his 1 tonne van a round and when he goes bush ie. gunbarrel,canning, simpson and a lot more. so its had a hard life. Inside of motor has never been touched except tappet adjustment,injectors etc. turbo has never been touched.
He does his own servicing, changes oil and filters every 7500k's not the recommended 5000k's he uses vavoline lxd premium.In adelaide at the moment can be bought for under $12 for five litres he uses a repco trade line filter which when bought in packs of ten can get for about $5 each. when asked why he uses such cheap stuff says thats all he can afford and it works for him. Can't argue with that.So for $35 and a bit of grease it's a cheap service.I have the same vechicle but I use about $80 worth of oil and pay between$15 and $20 for filters and is serviced at 5000k's.
I am not suggesting anyone should do this but it has to make you think. I have no interest in vavoline or repco bla bla . Just thought
some one might be interested .
regards
al