The present article aimed to synthesize spherical silica nanoparticles (SNPs) from rice husk ash as an inorganic product, by alkali extraction method and to estimate the produced products cost. SNPs were prepared in pilot scale from rice husk ash (RHA) based on optimum operating conditions, previously resulted from bench experiments, namely 2.0 N NaOH at 100 o C for 2h reaction time and at stirring rate of 120 rpm. The produced SNPs were characterized by sharp peaks of silica, amorphous spherical shapes, particle sizes of 18-75 nm and surface area of 200 m2/gm. The infrared spectra (FTIR) data supports the presence of hydrogen bonded silanol group (Si-O-H) and siloxane groups (Si−O−Si) in silica. The manufacture of the target product SNPs is thoroughly investigated economically, taking into consideration the production of sodium sulfate fertilizer as by product and using the residual RHA in bricks manufacturing. Techno-economic study was carried out covering the process design for the production line via characterization of the principal equipment and related utilities through detailed material and energy balances all over the process's steps. For total productivity of 5400 ton/year of silica, 60,264 ton/year fertilizer, 7,800,000 sand brick unit/year and 7,600,000 cement brick unit /year, the estimated total capital investment was 38,535,000 L.E , as well as the unit product costs of the principal product SNPs was 50 LE/kg. Further, a profitability analysis was assessed in terms of the return of investment and the pay-out time for the production .