When it comes down to the nitty gritty, both forms of forced induction cost about the same. The turbo kits have a higher price because they are a kit, and include much more than the turbo(s), intercooler, headers. These other parts of the kit vary between companies. Usually a complete fuel system setup is included: meaning new pump, injectors etc. Usually an bigger MAF meter, plug wires, calibrated comp chip etc. I don't know of many superchargers that give you half of that stuff in their kit.
Both have their advantages and disadvantages, NOTHING IS A FREE LUNCH. I admit that superchargers are less hassle installing, and are easier to deal with. You want to step up performance, just change the pulley. I like turbos because the boost is only there when I want it, I can run the stock, or small camshaft which is good for the street. Also, at a light the other person has no idea I have a pair of turbos under the hood, whereas usually you can hear the whine of a supercharger. There are many other reasons, but I will cut this list short for now. Everyone is entitled to their own choice.
BTW just to add some fuel to the fire: There are more turbocharged race cars than supercharged; and i'm not talking just Ford or domestic. Think about that one
