Simple carbon systems can cost well under $200, while premium tankless RO can run several hundred dollars. Choose from contaminant scope first, then compare annual cartridge cost.
Carbon systems
Direct-connect or dedicated-faucet carbon systems are usually the cheapest under-sink category and can be excellent for chlorine, taste/odor and selected certified contaminant claims.
Ultrafiltration
UF adds finer membrane filtration without RO reject water. It typically costs more than simple carbon but less than premium RO.
Reverse osmosis
Tankless RO systems from Frizzlife and Waterdrop often land in the mid-hundreds and add pumps, smart faucets and proprietary filters.
Installation
DIY installation can keep project cost close to hardware price. Hiring a plumber adds cost but may be worthwhile for drilling, tight cabinets or complex plumbing.