I moved 18 months ago to a house with a water meter, old cost per year about £300, now on water meter with 350ltr a day usage cost is £650 per year, I run a 300gpd at 50/50 waste to pure, I kept reading that will kill off my membranes as you need 3 to1, but 18 months later they are still going fine.
To get 50/50 remove the restrictor and fit at thumb tap and adjust to suit, keep checking pure/waste flow and tds to get desired results.