I also had severe nipple thrush with my first, was on diflucan for a month. My GP got me an authorisation number, so i think it was around $50, not $400 - $500.

It was 3 years ago, so i can't remember all the advice i was given from the GP and LC at the time (def. go and see a LC - it really helped!), but i'm sure if you search for threads you can find it. There is that purple staining paste (had a mental blank of them name) you can get which is incredible for getting rid of thrush. I think you can still get at the RCH in Melb from memory.

Also RayRay had a similar experience to me with bad thrush, so i'm sure she can help out also.