Any AC/Climate Control people know how the energy costs of modifying humidity compare to those of modifying temperature?
Depends on how you do it, of course.
The typical pre-energy codes way was to cool the air below the dewpoint with a regular A/C cycle then reheat using electric heat (or another heat source, if readily available). That is very cheap to install but very energy-intensive.
The "weedy little freestanding units" do essentially the same thing, but use the hot gas from the compressor to reheat the air. This doesn't cost much more to install (the refrigeration controls used to be the tricky part) and uses a little less energy than regular air conditioning that rejects the heat to outdoors because of the lower condensing temperatures. Larger packaged A/C systems can usually provide this as an option, but the extra cost is not often spent. (Most of the hours needing dehumidification need cooling too, so why add reheat for those few hours a year when it's 75F and raining?)
More sophisticated systems use dessicants to dry the air, which is regenerated by passing exhaust air across the dessicant and/or heating it. This uses very little energy, but is pretty pricy to install. Still, it's a popular choice as part of a "energy recovery" systems for those wishing to score energy efficiency points.