said by beans :
Even at 305 mbps, depending upon what you download, you won't get to the cap faster then somebody with 20 mpbs. You might get the file faster, but unless you are doing multiple streams of porn or bitthieft then you won't hit the cap if you are just doing single streams of anything.
Yes you can quickly reach 300GB with legal services.
1. Online backup services: Carbonite, Crash Plan, etc.
2. Streaming/downloaded HD media: Netflix, iTunes, Amazon, Vudu,etc.
3. Game purchases: Steam, Origin, etc.
With a household of moderate users, the bandwidth usage will be very high. You're paying for a faster connection because you use a lot of bandwidth. Someone contempt with a 20 Mbps connection isn't someone pushing several gigabytes of data a day.