BTW, comparing bandwidth to a commodity like water (or cars or roads), to me, is a bit daft. Bandwidth is infinite, unlike water, petrol, cars or roads.
The size of the ISP's (hose) pipe is finite (to an extent)
Simply not true. Bandwidth is not infinite. Let's do a quick sum - in this sum I will assume the entire capacity of the cable is available to South Africa (it's not) and there is no overhead.
Capacity: SAT-3: 120 Gb/s , SAFE: 130 Gb/s , SEACOM: 100 Gb/s --- Total Capacity: 350 Gb/s
Gigabytes available per second: 350 Gigabits / 8 = 43.75 GB/s
Gigabytes avaialble per minute: 43.75 GB/s * 60 = 2625 GB/m
Gigabytes available per hour: 2625 GB/s * 60 = 157500 GB/h
Gigabytes available per day: 157500 GB/s * 24 = 3780000 GB/day
Gigabytes available per month : 3780000 GB/s * 30 = 113400000 GB/month
Gigabytes per capita per month: 113400000 GB/s / 45, 000, 000 = 2.52 GB per person per month
So assuming South Africa had all the bandwidth on those cables AND they manage to use it evenly (without spikes and or lows) we have at MOST 2.52 GB per person per month available. No if we only take the internet using population we have at MOST 25.2 GB / person/ month ... and this is a highly theoretical number. This is the super upper limit at the moment. Of course the real limit is lower (due to various stuff I just mentioned) but also because a lot of bandwidth is used for other applications that has nothing to do with consumer ADSL (e.g. research, company data interchange, SA hosted content accessed from overseas) etc.
This by the way not only that affects us here. Network engineers have to jump through insane hoops to work around bottlenecks in the backhaul networks. Google bought a bunch of dark fiber routes, all the big players distribute data centers to to minimize bandwidth and power cost, companies like Akamai helps companies push content as far as possible to the edges of networks.
Of course .. I think we are pretty close to having more affordable internet, and for some users at least the experience of "uncapped". But no way that there is enough bandwidth to have everybody download hundreds of gigabytes per month.