Let's look at the real cost: price less VAT = £8.50 per 24 cans; price per 440ml can 35p; excise duty per can 25p. The cost of manufacture, transport, handling, and retailing works out at 10p per 440ml can (£2.40 per case of 24).
This sum cannot cover the costs of the can and transport, never mind the product. Either the supplier is supporting the price or the multiples are selling below cost.
The government should intervene and stop these ridiculous deals that encourage binge drinking.