Depends on what size you want.
Ours was under $5000, but a truly great day.
We had a celebrant on Sydney Harbour, then hired a boat for 4 hours which cruised us and 35 guest's around the harbour with a beautiful lunch.
For those of us who wanted to keep on going we headed to a hotel bar.
No table settings/chair covers/music/mc in sight.
Just think outside the square.