<p>Although protected cropping achieves high efficiency to maximise the yield of vegetables, growers tend to overuse fertilisers in greenhouses. This study evaluated the effects of fertigation levels [electrical conductivity (EC) 1.0, 2.5, and 3.5 of nutrient solutions] on the leaf gas exchange, postharvest quality, and nutrition of capsicum to determine the fertigation efficiency for two capsicum cultivars in a high-tech glasshouse. In addition, we extend the agronomic perspective to encompass an economic analysis, assessing the cost-effectiveness of adopting advanced fertigation strategies for greenhouse capsicum. Our results showed that High EC treatment did not improve mophorlogical and post-harvest parameters but decreased the nutritional quality, particularly Ca²⁺ and Mg²⁺, of capsicum leaves and fruits. Similarly, the postharvest quality traits did not improve with high nutrient supply. The highest net present value (NPV) and benefit/cost ratio were recorded in the EC 2.5 scenarios, reaching 529.6 USD·m⁻² and 3.35 in Australia, and 60.4 USD·m⁻² and 2.53 in India, respectively. The modelled commercial-scale capsicum business in Australia was expected to break even after 5.73 to 7.11 years; comparatively, the payback period in India takes slightly longer 5.96–8.31 years. Sensitivity analysis revealed that a 10% yield decrease results in more than 20% of economic loss in Australia and more than 30% in India. Overall, a higher level of fertigation at EC 3.5 did not improve the capsicum fruit’s nutritional properties or economic return. We suggest that the trade-off between fertiliser usage and yield has profound economic implications for the sustainable production of greenhouse capsicum.</p>