You should be thankful that Ph.D. students, paid so little, subsidize your classes and the research that makes the culture and science and technology of this country and world go. Often they are teaching 8 or more classes a year for under 20k, with 300-400 students paying, say, $2k per person per class. So, they are in essence generating as much as $800k/year for $20k, and on a much lower estimate of classes taught, they might still be generating ten times what they cost. That's why administrators want so many of them. And then they make almost equally cheap, exploitable labor for administrators when they become adjuncts after graduation, whether stopping with the M.A. or getting the Ph.D. Fortunately, their unemployment rates are minuscule.