My brother (in Wanganui) got a vodem, with no plan. I looked at the Vodafone website to work out how to top it up 2GB and what it'd cost, and I can't find it.

This page is the best I can find. It says what the vodem costs, but not what it costs per month. The only thing I can see is top ups,  $10/100MB or $30 for 512MB, but that can't be right, I want the base cost not the top up cost, 1GB is $20 on 2degrees and 3GB is $50 - but only where they have their own towers, else it's $500/GB when roaming.

Also, this page suggests $40/month for 512MB. That sounds too expensive.

Can you put a 2degrees SIM in a vodem? Not that it would help in this situation, Wanganui isn't a 2degrees broadband zone.

How do regular consumers work this out?