Bridesmaids only in Double Bay (Sydney) is having a one day sample sale on Thursday 24 September between 3pm-8pm.
You do need to pre-register from what I can gather - info is in the link.
Dresses start at $30
Nothing over $150 in the sale
I wore a bridesmaids dress from this store and its amazing. They have a lovely range of evening wear that can be worn to other parties and formal events.