For me, the real waste is the water pouring down the drain that is rejected by the membrane. I have to pay not just for the water, but a drainage fee meant to replace aging drain systems, that is based on the amount of water going through my meter, not just what I actually use.
I go through at least 170g a week, and with just over 400g in containers in my service room already, I have no room to store any more just to use in my gardens in the all too short summer gardening season.
For a very modest outlay, the used purchases of the main units, the used cartridges, and the chemicals needed, I can recharge and supply large quantities of DI
water for my systems.
THE REAL KICKER NOW, is that I don't have to use either anymore.
I discovered that the tap water in my city is good enough that all I have to do is age the water for the chlorine to dissipate, so for the last few years I've not used anything on my water.
I am keeping all the tap water purifier equipment though just in case conditions change.