Using students' process data from the game-based Intelligent Tutoring System (ITS) iSTART-ME, the current study examines students' propensity to use system currency to unlock game-based features, (i.e., referred to here as "spendency"). This study examines how spendency relates to students' interaction preferences, in-system performance, and learning outcomes (i.e., self-explanation quality, comprehension). A group of 40 high school students interacted with iSTART-ME as part of an 11-session experiment (pretest, eight training sessions, posttest, and a delayed retention test). Students' spendency was negatively related to the frequency of their use of personalizable features. In addition, students' spendency was negatively related to their in-system achievements, daily learning outcomes, and performance on a transfer comprehension task, even after factoring out prior ability. The findings from this study indicate that increases in students' spendency are systematically related to their selection choices and may have a negative effect on in-system performance, immediate learning outcomes, and skill transfer outcomes. The results have particular relevance to game-based systems that incorporate currency to unlock features within games as well as to the differential tradeoffs of game features on motivation and learning.