My MJ NZ Pale was £20ish but I needed to add 1kg of brew enhancer to it so say £5. That would be £25 for 40 pints or 63p per pint (so a bit more than your calcs above suggest)
I would say an AG brew would be £5 for malt, maybe £5 - 10 for hops, £3-5 for yeast so say £15 ish. That would be...