You mean after they've paid the rent, car loan, and everything else, normal people have 12000 quid to spend on a camera lens? That's a strange definition of normal.
Car loan? The bus is cheeper and you can have a sleep on a bus. And you can buy a decent car for under £2000 (mine was exactly £2000) if you really need one and can't use the bus. And yes, a normal photographer should be able to afford one a big white. For some it'll be nothing, for me I can do one a year, for others it might take three years. But for a wildlife shooter you are likely to have more than one and it shouldn't be unthinkable on a forum full of photographers that that is an expectation. Especially not in a thread about these lenses.
Normal wage here starts at £18,000 to £26,000 per year with £500/month to rent for a 2-3 bed house, £160 council tax, and £200 to food, with £120 covering 4 weekly bus passes. A photographers wage should be way higher than that I should hope. The normal monthly expense for a person is £1000/month assuming they are living alone in a 2 bed house.