It's the law of diminishing returns Steve.
A £12 bottle might be noticeably "better" (depending on personal taste) than a £6 bottle?
A £20 bottle might be head & shoulders "better" than the £6 bottle (depending on personal taste)
But it's highly unlikely that a £600 bottle is genuinely worth the money.
However, rich folk like to think that with that wealth, comes good taste
Hifi gear is another absolutely classic example. For a while I nearly was "That Tw@t" that claimed he could hear the differences between a £50 cartridge (needle) & a £250 cartridge. Or a £300 amp V's a £2000 amp.
And I was purchasing the stuff secondhand.
The folk that purchased it new are invariably exactly like wine snobs.
But God bless em. Without their constant need for the latest gizmo recommended by What HiFi Magazine etc. There'd have been no lightly used kit for folk like myself
In the real world, there's a massive difference between a Tesco brand £49.99 mini system & a £399 Panasonic all in one system. A set up made up of separate items costing £1500 is better still.
After that, every £1000 invested returns tiny gains in sound quality. But plenty of folk still do it, & claim to be able to hear an enormous difference that more than justifies the price. Therefore (in their mind) setting them apart from us Plebs......