The list is long, but I think my most pretentious beauty buy has to be the Guerlain Wulong Meteorites pressed powder. It was a limited edition of the Meteorites, but as a pressed powder in a refillable compact.
Normal price was around £110.
Runner-ups include:
Numerous Guerlain Meteorites (I collect them - which I guess is pretentious enough in itself).
Guerlain Rouge G lipsticks (they aren't even that good), and I hate applying lipstick when out and about so the fancy packaging is a bit pointless for me.
Tom Ford lipsticks, including a mini with my DH's name from the lips and boys collection (again, they aren't even that good).
Tom Ford Black Orchid perfume (I read somewhere that Tom Ford said that Black Orchid was intended to evoke a "man’s crotch", so maybe the pretentiousness has gone out the window with that).
It does last for ages on me - which I guess is unfortunate as DH absolutely hates it.
Aesop Parsley Seed Serum - it was nice, but I'm not buying it again for £49.
I also have a limited Guerlain perfume called Guerlinade, from 1998. Bought on sale as a teenager. I used it a few times, but didn't really love it, but also don't want to bin it.