Good response by Ed Valentine on this subject.
If I may add some possibly relevant detail...
Liquid cleaning agents may indeed contain water, but not necessarily to "dilute" the product for nefarious reasons.
First, as Ed implied, water may not be the reason a liquid product is a liquid. Many surfactants, solvent additives, fragrances, builders are anhydrous (water free), and still exist only in a liquid state at room temperature. Many pre-conditioners used for carpet cleaning may be formulated with components which are primarily liquid, with the addition of some powder. It simply is not an option for the formulation to exist in a free-flowing powder dry state. Yes, water might be added, but it is only done so that the initial mixture isn't like a "cake-batter" or paste consistency, and can be poured out of a bottle.
Secondly, water may be added to some formulations to aid in solubility. Imagine, if you will, a formulation that can exist in a dry state, dilutes with water, and cleans really well. However, the user has to struggle with getting the powder to dissolve within a few minutes. Or worse, the powder takes many tens-of minutes to dissolve. Such is the case with a lot of good crystallizing polymers used in encap formulations. If the product is difficult to dissolve, chances are the product will fail in the marketplace, even though it is a shame that it cleans and encapsulates well.
The manufacturer of course will pre-dissolve the product to a usable state, yes...using water. Water being the same solvent the user will choose for the final dilution.
So, when you compare your costs, amke sure you factor in every variable, and don't dismiss a product just because it is a liquid.
Yes, do take into account the shipping costs, but also consider the following...
1. How well the product works. Must you spend more time with a cheaper product for the same result, or worse?
2. What is the final cost per square foot, using all the hard costs? (including shipping)
3. How easy is the product to handle? (mixing, dissolving, foaming, measuring, proportioning in a Hydroforce)
4. What are the effects on your equipment? Does the formulation contribute to clogging, scale, fitting corrosion?
I think you will find that simply choosing on the basis of dry shipping costs is an insufficient evaluation criterion.