Opinions on uber expensive face creams etc

Very little would happen. There are only a finite amount of ingredients in the world and many of these products share the same basic ingredients with very reasonably priced products. Very often people are paying for a nicer texture, scent, and exclusivity, rather than efficacy. Often a parent company like Garnier owns both budget and expensive brands and the products are produced in the same factory and simply packaged differently. I don't mind paying a little extra for a nicer product, but some items are nothing but an exploitation of the gullible who buy into the pseudo scientific stuff the cosmetics companies use to promote the idea that these things perform miracles.

I remember reading a road test where a tester applied Creme De La Mer to one side of her face, and basic Nivea Creme to the other for six weeks and when before and after specialist photography were compared, the Nivea side was found to have been better moisturised and had a reduction in visible fine lines.

I've a dermatologist in the family who confirms the above and iterates the simple fact that the very best thing to do for your face is to use sunscreen. It won't stop expression lines or gravitational sag over the years, but it'll hugely reduce other wrinkles and signs of aging. If expensive creams did every thing they said, no one who used them would ever look older.