Like most modifications---it is not an investment. Nobody buys a supercharger thinking that it is adding value to their car, so the relative cost of the conversion to the value of the car is immaterial. The cost of the conversion must be related to the value that the potential buyer places on the results - a faster Maserati 4200. If it is worth $15k or $30k for that matter for the buyer to have a 4200 that can keep up with his GTR buddies, then they will be a buyer.
The commercial viability of the project would then be a function of the cost to research, design, test, manufacture the kit and the number of buyers who value the kit enough to purchase it at a certain price point. If there are enough buyers to recoup the investment then it is commercially viable. Nobody is suggesting that a maker is going to be supporting themselves on these kits but so long as they don't lose money, a shop like FD would add this to their bag of tricks. They make a bit of profit and gain notoriety for having done something few others have accomplished.
06 Coupe GT