its not the tradies wages, builders generally set the prices, tradies dont get a say, all they can do is shop around between builders to get better rates. When builders advertise houses to buy/build they need to guesstimate what the price to build is going to cost by the time the job is underway and completed, if theres price rises in the materials eg bricks, tiles or steel, the builder has to wear it.
IMO its a combination of a downturn in people buying and land prices decreasing and the building market being so competitive, they need a lot of people building to justify the amount of office staff and the higher salarys
