Well you can see how they manage their incentives so that for now:
1. Move to 1Gbps plan for $90 on a year and you get unlimited data. Normally this is $30 a month. But if you use their gateway for $25 then you get it for free.
2. More strangely if you get the $70 plan for 300Mbps you have to pay for the $30 so in effect you triple your data and it costs you less. Figure that out!