Word for people who buy things because they are more expensive/ for the brand
Solution 1:
People who only buy things made by famous labels are often called brand conscious. People who buy things because they are high quality are called quality conscious. I would use brand conscious also for people who buy things solely because they are expensive (I believe they are largely the same set of people). You certainly can't use the word price conscious because that means people who buy things because they are inexpensive.
If you are looking for a less descriptive and less neutral term, you could call these people snobs.
Solution 2:
I've heard label whore and brand whore used to describe such people.
Both from urban dictionary:
brand whore Someone who buys and prominantly displays name brand products (or products that feature large corporate logos) under the belief that such loyalty to a label or corporation is a chachet and brings prestige to their otherwise lack of taste, regardless of the actual quality or value of the products.
label whore A label whore is someone who only wears brand name clothes, with the name of the brand usually placed somewhere for all to see. A walking advertisement for a clothing store or brand.