Bunnings - Skills brand Cordless Circular Saw (without battery pack) $5
Only $5 but without the battery pack...
I am not sure how much the battery pack is but it is also stocked at Bunnings. No matter what it is, it works out to be a very cheap circular saw!
I can't find a picture or link on the Bunnings website.
So you will have to find it in-store :)