Sawyer filters are a sound investment since each one can provide up to 500 gallons (1890 litres) of potable water a day, and can last 10 years or more. A single filter
can provide for a family or a community at less than a fraction of a penny per liter.
Sawyer filters are also a one-time only investment since they can easily be cleaned with the provided backwash syringe, there are no catridges to replace, no moving parts to break, and no power source needed.
Here's how the cost per liter breaks down at 7 liters per day per person: