The present article aimed to synthesize spherical silica nanoparticles (SNPs)from rice husk ash as an inorganic product, and to estimate cost of the products production. SNPs were prepared in pilot scale from RHA using optimum operating conditions, resulted from laboratory experiments (2.0 N NaOH, 100 o C, 2h reaction time and stirring rate 120 rpm). The produced SNPs are characterized by sharp peaks of silica, amorphous spherical shapes, particle sizes of 18-75 nm and surface area 200 m2/gm. 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 RHA in bricks manufacturing. Techno-economic study was carried out for 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.