You should be able to rely on your quantity surveyor, so it’s a shame that you can’t. I usually test prices through informal channels:friends and family, forums I’m on and so on. Usually there is someone out there who has done similar work before. If you see a trade that you’re going to need doing work in another building, ask someone in the building what they paid. Why would they be secretive about that? And by striking up a conversation, you might develop a network of people who refer good trades to each other and share information that is more accurate than the info you’re getting from the QS. By the way, has anyone told the QS about the estimates in his work that were so inaccurate? How is he going to know and improve if you don’t? I’m not suggesting the work of a QS is easy. We had a piece of work done last year that was quoted at $32K by a local electrician on Sydney’s northern beaches. Same piece of work was quoted at $17K by an electrician from Sydney’s Western suburbs who had to travel for more than hour each day to get to the job. How can a QS give accurate estimates when quotes vary by that much?