Shower gel became popular a few years ago probably because more people take showers than baths these days, but there is some controversy about the ingredients in shower gel. It seems to me that you are paying a lot for the water and bars of soap are considerably more economical.
Note: If you look at the ingredients in your shower gel the first (highest content) is water and the second is sodium lauryl sulfate which is used to produce foam in shampoo and body washes.
Shower gel: $3 - $8 15 oz bottle
Bar Soap: Under $3 for 8 bars (each 4 oz and no water)