The price on the styles is fair considering the INCREDIBLE work that goes on them, I just finish making styles for Korg, and let me explain it more or less.
Basically there are 2 parts,
1.- The creativity on the idea in how the style is going to sound, orchestration, tempo etc. if it is ethic to RESPECT the natural musical phrasing, etc.
2.- the technical and huge amount of time to DETAIL the style in EACH part like the Bass, Chord1, chord2, Phrase1, Phrase2, Drum1, etc.
Most manufactures, like Yamaha, Ketron and Roland, if you want to create "Factory style" quality, is require to use a "special" software, property of each of the manufacturers, and mostly use ONLY by those designers, the ONLY brand that I know until now, Korg allows you to make factory quality styles WITHOUT that special software, what is a most in ANY case, is to use a PC Sequencer like Sonar, CUbase, etc...
Now that I have been in both sides, I have became aware of all the work that involves to make a GOOD style, that is why i said that at that price, is very fair.