[gfmucci]

The primary reason for the price difference between drinking water (potable water) and recycled water (irrigation water) is this: Irrigation water is not processed through the sanitary sewer system. It goes directly into the ground. It is not treated at a sewage treatment plant which is a big expense. Potable water goes into the sanitary sewer system piping system (through the drains in your house) and has to be be treated in the sewage treatment plant.

There is much greater expense in the overall processing of potable water than irrigation water. The price difference also acts as an incentive to use recycled water for irrigation instead of potable water, although I'm sure some of us (including me) bite the bullet and spend the extra few bucks using potable water to water a few plants when we don't want to do the "overkill" of turning on the irrigation system.