Gamified eco-points and cost salience-when rewards "do" and "do not" align in anti-food-waste apps

Anti-food-waste apps increasingly use gamified "eco-points" to nudge sustainable choices, yet when rewards align-or inadvertently fail-remains unclear, particularly under high price salience. This study examines how gamification, cost salience, and platform-trust cues shape consumer intentions toward sustainable food platforms. This study used an explanatory sequential mixed-methods design. First, three semi-structured expert interviews (interaction design, food co-op operations, and secondary education) were open-axial-selectively coded to surface design levers and pain points. Next, a cross-sectional survey of Taiwanese consumers (N = 256; 5-point Likert) assessed cognition, platform demand, reward perceptions, trust/traceability cues, assortment, and price acceptance. Reliability and construct adequacy were strong (Cronbach's α = 0.949; KMO = 0.938; Bartlett's χ ² = 5353.75, df = 435, p < 0.001). Exploratory factor analysis extracted four components (63.09% variance). Consumers endorse platform potential (M = 3.94), rate educational content (M = 4.10), and third-party product certificates/traceability highest (M = 4.27). Willingness to pay a price premium is modest (M = 3.32), indicating cost salience as a key barrier. Eco-points are viewed favorably (M = 3.92), but, in importance-performance map analysis (IPMA), rank below reliability information; transparency gaps (e.g., missing test reports or real-time verification) erode trust. The four-factor structure captures (1) sustainability cognition, (2) platform enablement, (3) reliability/traceability, and (4) cost/education salience. Occupation moderates platform demand, F(10,245) = 2.281, p = 0.014, with finance/insurance respondents showing higher demand than public-sector and retired groups. Rewards align when foundational trust-and-perceived value are strong, and costs are not front-of-mind; when price salience is high, transparent reliability cues and educational framing dominate behavior, and eco-points function best as supportive-not primary-motivators. Design implications for anti-food-waste apps include: (a) prioritize real-time verification, third-party certification, and end-to-end traceability; (b) pair eco-points with cost-offsets (e.g., bundle discounts) to blunt price salience; (c) expand assortment to reduce search costs; and (d) ensure fast confirmations and in-app customer support. Limitations include a Taiwan-focused, cross-sectional sample; future work should test experimentally and across cultures the causal interactions between rewards and cost salience.