<p>Students’ motivational beliefs, specifically, their achievement goals and cost perceptions, were examined in undergraduate introductory physics (<i>N</i> = 877). Prior research has shown that the combination of students’ achievement goals and cost perceptions may be influential in determining important academic outcomes. We focused primarily on students’ motivational barriers to success (i.e., maladaptive combinations such as performance-avoidance goals and high cost perceptions) within competitive college courses in science, technology, engineering, and mathematics (STEM). Results of path analyses indicated that performance-avoidance goals were positively related to high levels of cost perceptions, and that emotional cost mediated the relations between performance-avoidance goals and course grades. Neither mastery approach nor performance approach goals were related to any dimension of costs. Findings support the conclusion that the combination of performance-avoidance goals and high cost perceptions may be particularly deleterious for students. Implications for instruction and student success are discussed.</p>