Mobile Broadband is now offering superfast speeds with 4G available on some networks such as Telstra, Optus & Vodafone but remember speeds can depend on where you live & connection speeds can be pretty bad in some places (esp outside cities). So always check with your local dealer to see which is best in your area.
Or even better borrow a friend’s mobile to check coverage/reception/speed.
Cheapest Prepaid Mobile Broadband
Yomojo Mobile is one of the cheapest for Prepaid Mobile 4G Broadband.