I have two designer bags (Balenciaga city and Marc Jacobs Venetian that I use as a bookbag) that I bought with money saved from summer jobs, graduation money, and birthday/Christmas money.
I also am NOT one of those college kids that wears tracksuits to class! But I do always feel over-dressed. I have a lot of low-end designer clothes like designer jeans (Acne, Superfine, J Brand, etc.) and Marc Jacobs tops, stuff like that.
I guess the reason why I have expensive clothes for my age (I'm a junior undergrad) is because I look at clothes as an investment. I started buying higher quality clothing in high school because I knew I'd wear it longer than if I bought a high volume of cheap clothing that I'd wear once or twice. Where my peers would buy 20 tops from Forever 21, I'd buy a pair of Sevens. Over time, my wardrobe has accumulated and I still wear stuff I bought years ago.
I don't feel as though I do this because I want to "keep up" with adults, but rather because I look at clothing as an investment. I only buy expensive items that are classics (think black blazers, a little black dress, etc.); trendy items I buy from high street stores like Zara or Urban Outfitters.
As a side note, there are lots of girls at my university that wear tracksuits and carry real designer bags, but it's mostly due to the fact that there are a lot of wealthy students at my school and the fact that they want something designer, but don't have a true interest in fashion. Like, they see a bag a celeb carrying in US Weekly and then they buy it.