If you compare the price of beer in leading supermarkets, you can see that beer is, unsurprisingly, considerably more expensive than mineral water. It is only by comparing the most expensive mineral water (Perrier) with the cheapest beer (Tesco's Everyday Beer, which at 2% ABV is closer to water than beer) that the 'beer is cheaper than water' claim has any grounding in fact at all. (NB. This graph is not supposed to show a linear progression; it merely shows the lowest and highest prices available per 100 ml.)
This is surely a case of comparing apples with oranges. If you want to compare the price of products, you either compare the average price, or the cheapest price, or the most expensive price. You don't compare the cheapest brand of one product with the most expensive brand of another product. That is what is known in the philosophy of science as 'dishonest'.
In any case, hardly anybody drinks Tesco's near-beer, and whatever alcohol problems Britain faces are not the result of people drinking prodigious quantities of extremely weak lager.
So what purpose is the '[very cheap] beer is [sometimes] cheaper than [very expensive] water' claim supposed to serve? Is the idea that people go into supermarkets to buy bottled water but come out with beer instead? Is it supposed to be a scandal that very weak domestic beer can be sold at the same price as very expensive, imported mineral water?
As the graph below shows, bleach is cheaper than beer under this measure, but that does not inspire me to drink either.
The real intention is, surely, to distract the British public from noticing that we pay 40 per cent of the EU's entire tax bill and are ripped off to an appalling extent by venal politicians who are in cahoots with state-funded temperance groups for whom alcohol can never be too expensive.
