Amazon is no stranger to discounting its services for college students. You've still had to pay for Prime by the year, however, which can seem wasteful if you're only on campus for some of the year. Thankfully, you won't have to pay more than you have to. Amazon has introduced a by-the-month option for students that asks you to pay $5.49 per month only for as long as you need it. If you don't need fast shipping when you leave for summer break or have no inclination to watch The Tick during exams, you can put that money to better use.
You'll need to prove your status by supplying a .edu email address, but you will get a 6-month free trial if you're new to Prime. And yes, the $49 yearly rate remains intact if you're confident you'll use Prime for long enough in a given year.
It's not at all surprising that Amazon would cut students another break. Amazon might make little to no money from Prime if you're a per-month customer, but there's a real chance you'll order enough products to offset that difference. And yes, Amazon is likely hoping to snag some long-term customers. Even if you're not a profitable subscriber while attending school, Amazon no doubt hopes that you'll like Prime enough to pay full price once you graduate.