Unless you had an agreement before the case was heard that the loser would pay all costs, you have to be guided by NCAT which rarely if ever awards costs and certainly not on this scale.
I have a feeling that the lawyer may be trying it on and, on that basis, I would be raising a complaint with the Legal Services Commissioner.
Lawyers don’t get to decide how much the other side of a dispute pays. That is up to judges and NCAT Members. Perhaps the builder has left the lawyer in the lurch and they are just trying to cover their costs.
But click on that link, talk to someone at the Legal Services Commission and take it from there. Keep us posted on how you go.