Development costs - perhaps 10 hrs on the dyno with a good tuner (if they were that consientious), not many parts required, say total development cost in the region of 500 quid. At 85 a time sold direct, that sounds like good business to me.
My objections to dynojet are that unless you are modding exactly as per the development bike, ie same pipe, filters, no internal mods, the stuff they sell you could still be way off for your bike.
I bought a set of drills for about 8 quid, the other 77 would buy a reasonable amount of dyno time. I don't object to lightly modding a needle with a file on a single, so all I'm missing is the CV spring, and I wonder why you need that if you alter the damper hole correctly.