Endorsed in principle
I would generally agree with this, although comparing broadband speeds with buying a kilo of sugar or a gallon of petrol is oversimplifying the issue.
The problem is that if this becomes law, let's say the providers are compelled to accept a sliding scale payment, they'll get less money, but the 'cost' side of their business will remain unaffected (and you can guarantee they'll guard their profit margins with their lives). So the only area of the equation that can be manipulated without falling foul of regulators or shareholders, is the quality of service.
With this as law, we can expect that the notional "speed" of the line will remain high (at least, averaged over a billing month) but the actual "throughput", in terms of what can actually be downloaded over this high-speed line, will take a royal kicking as the providers fight to satisfy both regulators and shareholders. We might end up seeing the sort of ridiculous manipulations where the providers will give us Gigabit connection speeds for approximately 2 minutes out of every 20; thereby boosting the average speed without actually enabling us to do anything useful. Or indeed Gigabit between the hours of 2 and 5am, in order to advertise a 100Mb line, averaged monthly.
<- Beer. 'Up to' a pint.