I was replying to OP who is building a house presumably on a standard industry contract. In Vic cost plus housing contract is prohibited except for exceptional cases.
Obviously in a cost plus contract margin is disclosed(only because as owner you are an open cheque book) but in all other cases it is a commercial secret regardless of whether it is a housing contract or a commercial building contract.
Willos74 writes
" I guess it sounds fair, but when you convert it to the fact he is going to make $65k from us...it kind of hurts a bit! "
In my view the above creates unnecessary negativity and discontent, only a stupid builder would discuss his margins with the client in a lump sum contract. What is there to gain? Nothing! What is there to loose? Growing seeds of discontent in the client and possible demands for concessions.