Ernie1 my software calculates this so it’s actually quite easy. These prices are for consumables only though, and don’t include electricity, labour, cleaning chemicals, investment, alcohol tax, VAT etc.
Ball park most brews probably come in at 80p - £1.50 per litre.
The cheapest is something lowish alcohol without much hops. I did a 3.2% mild that cost 81p/L.
Hops and fruit can be more expensive. The raspberry sour I’ve just done was £1.21/L.
Like most businesses though the fixed costs and overheads can be a large part of the cost.