The weather is free but has been pretty miserable so far this year!
Just about everything except petrol is more expensive IMHO.
I reckon you will need more than $80k with four kids.
I have 2 kids, I don't smoke, I rarely drink, I don't live on any benefits and I earn $80k and spend $80k.
However, the bottom line is that if you want your children to have a future move to another part of Australia or stay in the UK. There are no prospects in SA for young adults.
And to all the 'clever dicks' who respond to any criticism of Adelaide as if it were a personal attack on them ...Yes I know where the airport is and will be using it because although the UK is miserable cold and violent, there is culture , better education and a future, and you can't say that of Adelaide.