I have an RO, for reasons. It cost less than the cheapest espresso grinder that’s acceptable, but it has ongoing maintenance costs.
Edit - if you want to get nerdy, a permeate pump and/or high inlet pressure (which is largely out of our control) helps with the longevity of the membrane; I get about 2 years on mine and my intake water TDS is 500ppm; I replace around 75ppm outflow which is higher than “normal” but the water is designated safe to drink to begin with. Basically, the greater the delta in pressure between the inlet and outlet, the less waste is produced and the longer the membrane lasts.