It's an interesting question. To rephrase, I think the market is undersupplied with new construction skewed towards lower quality apartments. This would suggest that high quality apartments would be extra valuable.

I have less experience in the high end of the market, as it's firmly out of my price range. Perhaps that alone is the answer? If while earning ~2x median pay, I don't consider staying somewhere more livable it would suggest prohibitively high prices. I'm unsure if the price is dictated more by the aforementioned undersupply or the higher quality. It probably reveals something about inequality in society.

I can't be certain the motivations of the developers choosing to build smaller apartments, the reasons I alluded to in the parent comment were an attempt at an educated guess. There is however an obvious ground truth that apartment sizes are shrinking (47m2 2014/44m2 2015 for 1 bedroom -10% in one year!) [1]

- [1] https://www.afr.com/property/melbourne-new-apartment-sizes-s...