Earlier quoted context omitted.
Would be great if they standardised on 'price per year of use' like they do now in australia where food always has to have the $/100g or $/100ml in addition to the unit price. (Many supermarkets were basically rorting people by charging more for the 'bulk' items but labelling them as best value)
In Britain they also have some unit-price law. But Tesco blatantly abuses it: eg one kind of apple is priced by piece, the next goes per 100g (or per 1kg, but converting between 100g and 1kg is simpler).
You can see the same for the fixed price chickens vs the organic/free-range that are priced by weight.
Although Tesco will no doubt try to game the system, it is in their interest to show you understandable unit prices because they want to flog their stuff cheaper than the brands.