I would like to see the outcome once somebody here takes it to court in the UK or Germany.
To me it is not at all an "obvious mistake" to pay €1100 to fly BA's F to KUL. You can fly QR C for this price during a sale, and that product offers a similar seat and food to BA F - overall a very similar on board experience, and the ticket rules regarding flexibility are pretty similar.
It would be an obvious mistake if a fare was €41,34 instead of €4134, but paying €1100 for a longhaul premium cabin is very much normal - albeit for the initiated maybe more so in C than F - however I very much doubt it can be "obvious" to the general public, which is what a judge has to assume that the customer entering the contract with BA is.