i had one. we're on a well and the amount of wastewater was unacceptable. water is a precious commodity in Colorado and it's just easier to buy it at a store for 37 cents a gallon
I have sold/and used RO systems for over 2 decades. Ancient models were not very efficient (~ 1:4,
but that is based on low water pressure). New versions are very efficient
(more efficient membranes), especially when using a booster pump.
Importantly, what is the EC of your raw water... and the reject water?
Keep in mind, the reject water can be used to water garden plants, lawn...
Unless you shut off off the bath and dish water after wetting, you will likely waste far more water doing these basic daily uses than when making 10 gallons of RO
finally, if your store bought RO is from local sources...