A rough starting estimate to calculate HP gain is to take boost (say 5psi) and multiply it by 7% (a constant) to get your approximate power gain (in our example 35%). Why 7%? Because 7% is approximately how much more air and fuel gets into the motor with each pound of boost that is added. To get a more exact figure, take 1psi boost and divide by normal atmospheric pressure, 14.7psi at sea level. 1 divided by 14.7 equals 6.802%. Under ideal conditions, you can expect to burn 6.802% more fuel and air per pound of boost.
Air/Fuel/Horsepower you need XXX amount of fuel to support XXX horsepower at the proper ratio. So it would depend on how much power you’re asking your setup to produce at any given time. Example: Running the same setup, my father got 10mpg, and I got 6mpg. It wouldn't take Einstein to calculate who the more aggressive rider was. Bottom line is......takes fuel to make horsepower.
Pricing in our market segment works the same way is does in any other market segment, cost vs what is the consumer willing to pay, if your price is too high, you don't sell, and you're out of business.
As for potential performance all you have to do is look at the compressors (that's what compressor maps are for). You make horsepower with CFM so don't get fixated on magazine ads or internet squawk on boost numbers. What you really want to know is, how much will the compressor flow, at what pressure, and what temperature. The Rotrex C30-74 supercharger produces equivalent flow to the MCXs 16T and the Rotrex C30-84 supercharger produces equivalent flow to the 28RS. There is also a C30-94 but I don’t think MPI uses it in their kits…could be wrong…you would have to call them.