Companies that deliver customized solutions through projects are interested both in the efficient resource use in their manufacturing process and complementing a core product with services to fulfill customers’ specific needs, that is, efficiency value and service value. Firms face tensions, trade-offs, and synergies in aligning efficiency value and service value. This study focuses on the development and delivery of customized solutions in business-to-business (B2B) settings, aiming to uncover project actors’ perceptions of efficiency value and service value and the mechanisms used to balance them. A qualitative exploratory study conducted in two software companies and two shipyards reveals that service value and efficiency value are perceived through three aspects: benefits and sacrifices (from both short-term and long-term perspectives), related lifecycle phases and activities, and various enablers. Ten balancing mechanisms harmonize the tensions and trade-offs between these two values. Internal balancing mechanisms include standardizing, modularizing, configuring, reusing, and scaling. External balancing mechanisms comprise co-creating, negotiating, adapting, bargaining, and segmenting. These findings enhance our understanding of value perceptions from a dual-lens perspective and illuminate balancing mechanisms in project business and solution delivery. The examination of software firms and shipyards broadens mass customization research by providing empirical evidence from unconventional contexts.