Google vs cable....
They could just offer a lower upload speed... Don't expect many households really need the ability to upload at more than 20 Mbps (even if they have several security cameras running simultaneously).
US$ 70/ month (+taxes) for just internet and $120/ month for internet and TV may be comparable prices (not in USA, so don't know how well these compare with cable services) but seem costly to me. Given the choice of 100 Mbps (at say $35) and 1000 Mbps at $70, I would go for slower, mainly because of the price.
Google 'Free' service offering 5 Mbps/ 1 Mbps (from $30 installation and $0/ month to nominally $0/ month for 7 years, with $300 installation spread over first 12 months) seems an even better choice, for those who could later want higher speed, as pricing might reduce over time, and they could get it installed but use it in parallel with an existing service, or push it (with things you want to use it for, and see if Google kicks you off for breaking their AUP).
In the UK, if a service claims it's unlimited, a minority will test that. ISPs have sometimes done a U-turn on their "unlimited" service AUP when they consider the service is being pushed to overload, and have suffered the consequences. UK broadband comparison sites now include "truly unlimited" if that is the case, and try to determine any limits held in AUP details, such as some with a 100 GB/month limit which still claim to be "unlimited".
If a service claims "unlimited" nowadays, they need to be honest to consumers, and not expect the "< 20% will be heavy users" "business model" you've put forward, because with the growth in streaming TV, film services, and so on, traffic is bound to increase and that model is likely to fail in the not-to-distant future.