1) Yes. I am very interested in the content and prefer a high percentage of natural fibres.
2) Very unlikely. Partly because I seldom wear 100 % synthetic fibres. Partly because if it's from a famous brand, it's probably expensive, and I would rather spend that sum on items in fabrics I really like.
3) Not sure that I understand the question completely. But generally speaking, so-called designer items, or items from famous brands, are more expensive, and people therefore often expect the quality to also be high. However, you don't always get a high quality just because you pay a high price. So if you want good quality for your money, it's wise to learn to evaluate qualities, and to keep an open mind and try less known brands and also thrift shops.

@FashIntern - very interesting info, I will definitely do more research on the subject, thank you!
@ The Cat - is it true that we expect the quality to be consistent with the price, and it is very unfair and arrogant of some designers to be taking advantage of consumers' lack of knowledge or understanding of the subject. If the material is cheap, the whole piece is cheap. Period.