Build or Buy?? Which way works cheaper??

Hey everyone! I’ve got a quick question and would love your input. I’m not a first-time buyer, but I’m trying to decide whether it’s better and more cost-effective to build a home with a big company like Metricon or Coral Homes, or just buy an existing new build. I’m after a pretty standard 4-5 bedroom home on about 400 square meters of land.

I've had a look at a design I like from Metricon called the Lucca 35, which is listed at around $500k, but that doesn’t include turnkey finishes. What do you all think? Any advice or experiences you'd be willing to share? Thanks so much in advance!