Land and Build Costs
To me this seems like the biggest barrier for new builds. In 2021 I purchased a 500m2 block for $310k and had a large single story 4 bed, 2 bath, 3 entertainment areas build for $380k. Nowadays it looks like you would struggle to find 500m2 of land for close to that total price.
$300k builds now look like $450k and $600k up to over $800k just for building alone. So it is all well and good to encourage investors to buy/build new, but with current build times no longer being 3 to 6 months, I think this is going to be a huge blocker.