50 ppm Borates are a mild algaecide so in theory would let you target a somewhat lower FC/CYA ratio and that is where you would normally get the chlorine savings. However, actual algae growth rates vary especially based on algae nutrient (phosphate and nitrate) level. You generally should not be adding 50 ppm Borates for algae control or to have a lower FC/CYA level. You add 50 ppm Borates for the additional pH buffering, especially for SWG pools where it also helps reduce scaling in the salt cell, and perhaps you add it for some extra sparkle due to reducing the surface tension of the water.
If you really wanted to lower your FC/CYA level to lower chlorine consumption, then there are other ways of preventing algae growth, also at extra cost (the borates aren't free either) and that would be use of weekly Polyquat 60 algaecide or use of a phosphate remover. The specifics for costs especially for a phosphate remover are complicated because they depend on initial phosphate levels, whether there are phosphates in the fill water, the amount of evaporation and refill, blown-in fertilizer, use of phosphate-based (e.g. HEDP) metal sequestrants, etc. So the simpler approach is to not worry about phosphates at all and to instead have an FC/CYA ratio that prevents algae growth regardless of algae nutrient level. That is what the Chlorine / CYA Chart is set to do.
