Black-n-Tan, your idea that the Kopykake system pricing (& most other similar items) is BS & overpriced is quite correct.
Most food manufacturers (here in the UK anyway) are that paranoid about falling foul of regulations that they will dive into this sort of deal without even doing any research, & end up paying big bucks for "specialised" equipment & follow on consumables. Custom printers, scanners, copy systems & airbrush set-ups are all the same, but the food manufacturers still buy this stuff as it is all assured food safe.
Reality is that as long as you use colourings & carriers that are food safe (within the regs of you area), you will not have a problem & will save a fortune. Ready mixed "food paint" for airbrush use is readily available from suppliers other than the type you mention & also at a fraction of their price.
The only thing I would advise you watch is that you carry the "food safe" theory into the cleaning & maintenance of you brush (no thinners or regular grade lubricants in the airbrush) & also make sure that you have some form of filter on your compressor output.