Hey, I'm glad you're posting on here, man. I think you're a pretty good example of the college-student demographic that will be really interested in the INT once they find out that it even exists.
Once you're in-country and have your gear, hiking the trail is really cheap. Since you're walking everywhere, you won't have any transportation costs unless you decide to take a bus someplace. So the biggest expenses relate to where you choose to stay and how you choose to eat.
If you sleep outside every night, or stay with friends, then your lodging costs are zero. On the other hand, if you stay in a hostel every chance you get, you'll spend a lot of money.
Same goes for food -- it's possible to hike the whole trail eating only food that you buy from small stores in kibbutzim, etc. If you stick to that, then you won't be spending much more on food than you do normally. However, on the trail, you might be burning twice as many calories as you normally do. So if you don't want to lose too much weight, you'll eat a lot more, and if you're like me, you'll be tempted to eat at restaurants when you get the chance. When we stopped in Nazareth on our hike, we ate at the Tishreen restaurant and spent something like 300 shekels on dinner for three people. That was ridiculous, but it was one of the best meals I've ever eaten.
In short, once you're in Israel and have the necessary equipment, you can hike the trail for very little money. It's hard to give specific estimates -- maybe other hikers here can give some good methods of figuring out costs.