That is simply not true that operating at a higher FC at the same CYA will use the same amount of bleach. The loss is roughly proportional to the FC level for a given CYA level. If you maintain double the FC at the same CYA level you will lose roughly double the amount of chlorine and this will cost you about twice as much in chlorine cost. When you double the FC level (keeping CYA constant), you double the concentration of ALL the chlorine species -- hypochlorous acid, hypochlorite ion, and chlorine bound to CYA. The doubled concentration reacts twice as fast and breaks down in sunlight twice as fast.
While the initial dose for a phosphate remover can be somewhat costly where reducing 3000 ppm in 18,000 ppm using Orenda PR-10,000 would be (3000/10000)*(19000/10000)*$40 = $23, the maintenance dose to reduce even 1000 ppm per year would be only about $8.
So while the philosophy of not using phosphate removers and instead maintaining an FC/CYA ratio that prevents green and black algae growth regardless of algae nutrient level is simpler to explain and implement, it is not necessarily the least expensive approach. Also keep in mind that the use of phosphate removers is incompatible with using an HEDP-based metal sequestrant.
While the initial dose for a phosphate remover can be somewhat costly where reducing 3000 ppm in 18,000 ppm using Orenda PR-10,000 would be (3000/10000)*(19000/10000)*$40 = $23, the maintenance dose to reduce even 1000 ppm per year would be only about $8.
So while the philosophy of not using phosphate removers and instead maintaining an FC/CYA ratio that prevents green and black algae growth regardless of algae nutrient level is simpler to explain and implement, it is not necessarily the least expensive approach. Also keep in mind that the use of phosphate removers is incompatible with using an HEDP-based metal sequestrant.