Please come again.
The costs are direct and indirect, economic and environmental. Having a lawn and maintaining it requires inputs of energy and water, which usually must be purchased (it's not free). Even in areas where water is not metered (and thus appears to be free), there can be the costs associated with pumping the water to your location.
It's also the case that much of the energy required is fossil-fuels for operating lawn equipment. From this obvious use of fossil fuel to the not always so obvious use of fossil fuels for fertilizer, it's easy to see why it could reasonably be expected for this energy input to increase in costs, at least for the near future.
Of course there is also the time costs. Mowing, weeding, fertilizing, and watering are tasks many lawn owners find themselves busy with. The fertilizer we apply, which is supposed to make for lusher lawns also may mean mowing more.
