Though the $150 12 month plan works out fairly close to that price point ($12.50 per month), and comes with more data included (80GB for use anytime over the 12 months, which lands at 6.6GB per month average).
The other thing to watch out for, is there is a difference in coverage. Boost uses the full Telstra retail network, whereas Belong use Telstra "Wholesale" network. Basically a bit less coverage in regional areas.
* I am a Boost Australia customer. This is a peer to peer community where users help each other.