Can anyone tell me the difference between a student instrament model and a professional model? Why is a pro model so much more expensive?

Student models are usually, though not neccesarily mass produced. pro models are hand made by luthiers, master violin makers. you are paying for their time and the fact that they make them buy hand makes them far superior to mass produced violins as they take time. the woods used are also probably more expensive and everyhting is of a far better quality. they also have superior tone. better all round generally.
doesn't make your violin bad though. just affordable