[cauterized]

I wouldn't necessarily use the term "exploited" (I would save that for a different sort of situation), but you've certainly been put in an untenable position.

It sounds to me as if the problem here is not the pay grade but the expectations. Did you know what those expectations would be when you agreed to the project?

What you're expected to get done in the designated number of hours sounds to me as if it would be unreasonable at virtually any pay rate. Assuming the app you're building has a certain level of complexity, I wouldn't expect those results in that time frame from anyone less than the most experienced professionals. And it's obviously unreasonable to expect you, as a student, to work at an equivalent velocity.

My guess would be that the people in charge of this project don't actually understand the work involved in it. Either way, I would run, not walk away from it.