I think it's a really individual decision. For a looong time, I couldn't keep a scale in the house, or I got very obsessed with it. Now I'm okay having it around, and actually weigh myself every morning with little to no mental angst.
I'm a student too, and bought my scale for about $40-50 I think. It's just a basic digital scale - no fancy gizmos that tell you body fat percentages or store past numbers for me! Those are the things that tend to raise the price, in my experience.