FBR General Discussion, page-1085

You thin air guess is pretty much correct , these are the items not required by utilising HX :
Labour(brickies teams take roughly 3 weeks per structure)
Cement
Scaffolding
Sand
Wall chasing
There is no over ordering (therefore no collecting of lefter bricks)
There is no under ordering(therefore no extra deliveries)
Waste
Site clean costs
Storage shed for brickies cements and sundries.
Down time due to sickies , inclement weather.
Down time due to mistakes.
Insurance, safety .
What is the time component of a faster build worth to any builder atm ? A LOT let me tell you .
Site theft at brick up stage is a big problem .
Pre manufactured components ready to fit along the way and immediately after build is complete .

All this should be factored in as cost savings , the problem we have here in calculating the cost saving to the builder is that FBR have not realised any figures relating to FBR charges to Hire HX out for WaaS. I’m speculating Dale would have crunched his numbers , hopefully next announcement should make things a bit clearer .
Talk about waste and safety .