It is an interesting question. I did the sums a while back, in order to convince myself it was OK to buy a G40. At current prices it costs me about £20 for a 20 litre batch, ie 50p a bottle (£6 for 5kg Golden promise, £1.50 for 500g crystal, £3 yeast, £8 for hops, £1.50 odds and sods).
A nice...