Inner city 7 Eleven Stores are selling bike Helmets for $5 bucks each.
Melbourne City Council and the State Government are subsidizing these helmets to help the Melbourne Bike Share Scheme for a 3 month trial. There are no requirements to be a member to buy these helmets though. As per the article below, they are subsidizing around 8-10 bucks per helmet. (cost price around 15 bucks)
See http://www.theage.com.au/victoria/helmets-for-hire-in-bike-s…
I rank these helmets around the $20-$30 dollar retail mark in terms of quality (no brand names here). They come in different sizes and colours, and there is no need to be a member. You just rock up at any Inner City 7 Eleven store and buy over the counter. No Questions asked.
You can go to melbourne bike share's website to check out the Sale locations. The helmets are certified to be Australian Standard.
The good thing though is, if you decide to upgrade your helmet to a better one later on or don't like it after a while, or just want a replacement one, you can return it back to a 7 Eleven store and get $3 bucks back. So it's pretty much risk free.
The helmets themselves have an adjustable knob for the back strap (makes it very easy to adjust), proper padding inside, and a visor in front.
Someone below gave this link about Cheap and Expensive Helmets. Worth the read
http://www.bhsi.org/testbycost.htm
Thought the bike share thing was a good idea, but hampered a bit by needed to carry your helmet around, but this makes it much more appealing.