As an aside, this is classic HN: very authoritative sounding comment, voted right to the top, spouting complete nonsense.
So an example from a recent wholesale catalogue, 1 30L keg which you can probably sell 58 pints out of will cost around £150 so that gets your cost price of around £2.58 / plus VAT and beer duty and you're up to cost price of over £3.00 / pint
So margins are variable but as you can see if you want to sell at around the average price around the country which is £4 / pint then you're not talking about a massive margin.
The reason why food is a popular option for bar owners is that the breweries don't take any of the margin so the owner takes all the profit from food sales, plus in many ways, the food is extra income from people that would be taking up the space to drink too.