Picked these up on a clearance rack at Target near the end of the season - paid approximately $5 for a double pack. While they aren't the hottest in home decor, they get the job done, and are remarkably easy to clean and refill. The tank is small enough that it is not heavy when 100% full, yet large enough that it can go a few days (on the lowest setting) without being refilled. Even while constantly on, the filters have lasted a good three-six months, and are available just about everywhere for $3-5 each.