NNs spending too much money

I don't understand why they had to move to such an expensive suburb in Sydney, houses in this area are so expensive, and they bought a 10,000,000 house and a 15,000,000 house, they could have bought in a massive block near a beach in outer Sydney and build a house with a capacity for their family. If they did this, then they could use the rest of the money to live of in the future. I just don't understand.