300GB during the day sounds good - considering that 99% of my bandwidth is during the day. I can do the odd Steam updates at night.That's a bit hard to answer. And not even trying to be funny.
Remember that usage between midnight and 06:00 doesn't count. It's only day time usage that counts. So 600GBs during the day will make you drop a level on a business, 600GBs after midnight means nothing.
I find you can 300GBs(a month) during the day before dropping a star. And if you pull around 500GBs after midnight you can do almost 800GBs before dropping a star.
So I start all my steam downloads when I go to bed and hardly ever drop at all.
Now just to dig through feedback threads to see how uncapped home's performance is.