This gives you a pretty good perspective on how much different items cost per gallon.
http://www.cockeyed.com/science/gallon/liquid.html
tap water 41708928� $120.00 $0.00
Folgers Coffee (black)� 998.6 $5.50 $0.70
unleaded gasoline 128 $3.059 $3.05
Kool-Aid� 256 $3.69 $1.85
Clorox bleach 128 $2.20 $2.20
lowfat milk 128 $3.79 $3.79