"How come that suburb is so cheap then? The median price is about 300 according to API magazine.
Is there lots of housing commission or something?"
You would be hard-pressed to find anything for $300K in central Sunshine - entry level is probably low $300's and they go up from there. In areas directly surrounding (and still considered part of) Sunshine - Albion, Ardeer, West Sunshine - yes, you can pick up houses for high $200's/$300K - but not sure for how long, even in this current doom and gloom climate. Sunshine has fantastic amenities and great potential for future capital growth imho - as has been mentioned, it's just over 10km from the city, has some beautiful period housing (as does Albion, Ardeer), shops, cinemas, main road strip, great access to everything.
There is housing commision, but only in Sunshine West, as far as I'm aware. Crime - yes, that too - and a reputation, but honestly, there are worse places, and not to say it doesn't exist, but I think the media like to play it up to be honest.
My personal opinion is that is a great spot to buy, and still affordable.
Do some more research - you may be pleasantly surprised by what you find.
ETA: I am originally a Sydney girl, and no way could you compare Sunshine to Redfern. Redfern has, on many occasions, been a no-go zone for police, ambulance, etc etc - with riots in the streets. I have not seen anything like that in Sunshine!!! They are on two different scales imho.