The purpose of this paper is to investigate the economic sustainability implications of reconfigurable modularization and changeability in semi-automatic assembly systems using a system dynamics perspective. Through our applied research, using a multiple case study approach, we assess the potential and drawbacks of reconfigurable modularization to advance sustainable practices in the manufacturing industry with the purpose of improving overall long-term resource allocation in product realization processes. The traditional approach of developing and industrializing one product at a time is becoming obsolete due to factors such as more frequent product introductions, technological innovations, and sustainability requirements. This is due to the increasing trends of product variety and customization, which often necessitate costly modifications to production systems throughout their life cycles. To address these challenges, scholars advocate for the adoption of reconfigurable modular architectures in product and production system designs, facilitated through product platforming. However, when it comes to studies of the long-term economic impacts from the effects in operations, meaning the economic sustainability implications for the production system throughout its life cycle, there is limited research examining the economic rationale for this approach. Therefore, this paper proposes a systematic examination of the economic sustainability implications of reconfigurable modularization in semi-automatic assembly systems using a system dynamics perspective. By leveraging a system dynamics simulation, we structure and investigate the potential economic short- and long-term tradeoffs between the benefits and drawbacks of reconfigurable modularization derived from empirical findings across four case studies. The novelty of this study highlights not only the investment costs and related engineering implications and their costs but also the estimated operation costs encompassing multiple product introductions expected during the life cycle of a production system. We believe that such an approach offers valuable insights into how reconfigurable modularization can be useful from an economic sustainability viewpoint within semi-automatic assembly systems, thereby contributing to the ongoing industrial transformation towards sustainability.