Of course, $139 is far too high for a student.
Tons of students pay $100 for books. Tons of students pay $10,000-$30,000 for tuition.
But no students pay for software
I suppose many don't. I guess it depends on the meaning of "too high" for a student. I took it to mean "students cannot afford to pay $139" rather than "at $139, students will prefer to get the software illegally, even though they could pay if they chose to".
"Note: Mathematica for Students is intended for students enrolled in accredited academic institutions and is for use on a student's own personal computer."