Is there a word for people who buys things because they are more expensive or because they are specific brand or label?
These people don't buy the items because they are higher quality. They buy them because they want others to think they are "cool." These people can often hardly afford such items and this money could be better spent on other items.
This is opposed to other people who might buy more expensive things because they are of better quality. (Who would rarely buy popular brands because their prices are inflated simply because they are popular.)