Was it one of the big crowds ie Kresta, Vista etc? When we had timber venetians put in we got quotes from various places and the bigger companies were HUGELY more expensive. Like, thousands of dollars more expensive.

We ended up going with a small independent family company that were much cheaper, great service and did it cheaper for cash. I don't think they did curtains and sheer hollands (I'll look them up and if they do I'll PM you the name - this is when we were in SE Melbourne) but in any case I recommend getting some quotes from smaller companies after that experience.