There are a couple things that I'd like to recommend for students doing this research project in the future. First, make sure the wording in your survey is such that the question can't be misinterpreted. Otherwise, you can get skewed results. Also, don't wait until the last minute to start your calculations. This was the part that probably took us the longest. They're going to take you much longer than expected. Lastly, I wouldn't recommend using a site like surveymonkey.com, and the sending the survey out to students. We tried using this method and got a very low response rate.
I think an interesting topic could be one in which the idea expands on what we studied with textbooks and spending. I think it would be cool to go more in depth with this and study textbook spending not just in general with students at K, but take a look at spending by major, and look to see who spends the most on books, what majors buy their books where, etc.