they are expensive, require an expensive plumber to install, potentially another source for leaks, and require regular cleaning. i'd rather just pay $10/month for gallons and gallons of bottled water.
https://www.amazon.com/Whirlpool-WHER25-Reverse-Osmosis-Filt... that is $130 and the kits are very easy to install. In 13 months you'd have it paid off and you can make all the water you want.