The last time I looked at affordable RO units, the waste water ratio was more like 7:1 or 8:1. I believe the big commercial units can reach 1:1. How much do the 3:1 / 4:1 units cost?
Where you run into the excessive brine ratio is when people buy systems with bladder tanks but no permeate pump.
As the bladder tanks fills the pressure differential across the membrane drops proportionally.
With the decrease in pressure differential the efficiency of the membrane drops and the brine ratio rises.