The electrolyte significantly influences the performance of most aluminum-ion batteries (AIBs), where AlCl3 serves as the primary ion source. This study systematically investigates the effect of AlCl3 impurities on polyamide-based solid polymer electrolytes (SPEs) for AIBs, focusing on both performance and cost-effectiveness. SPEs are synthesized using a polyamide matrix and an ionic liquid (AlCl3:Et3NHCl) containing excess AlCl3. Six different purities of AlCl3 salts (98%–99.999%) with variable prices (€0.028/g–€6.198/g) are used for the preparation of SPEs. Electrochemical characterization reveals that variations in purity do not significantly affect the performance of the electrolyte, as reversibility, ionic conductivity (0.19–0.21 mS/cm), electrochemical stability (2.70–2.83 V), and Coulombic efficiency (98.0–99.5%) remain consistent across all samples. Specific capacities range from 28.71 to 43.50 mAh/g, with no systematic correlation to impurity content. The cost analysis demonstrates that low-purity AlCl3 (€0.028/g) performs comparably to high-purity salts (€6.198/g), leading to a 17-fold reduction in electrolyte costs. This highlights the economic feasibility of using lower-purity AlCl3 in AIB production, making large-scale manufacturing more affordable.