Historical sales data

I am seeking recommendation on the best value for money historical sales data for SA. I have found RP data, Australian Prop monitors and propertyvalue.com.au. These all seem to be $70-100 for a postcode with 2 years history. I used to buy the same data for $20 from http://www.homepath.com.au about 7 years ago, but now they only do home loans. I suppose things go up in 7 years but the increase seems excessive. Can anyone help with a recommendation?  I need postcode data across 3 postcodes on an ongoing basis and would be happy paying a monthly subscription if need be.