Because the 2500 in a family of 25000 is used for mass produced cars The 25 for GT racing is relative to the version not the family The FIA set a minimum of 25 homologated vehicles to prevent one off exotic special editions Let s look at some examples during the late 90s both FIA and ACO rules were permissive enough to allow cars such as the BMW M3 GTR and McLaren F1 LM to race The BMW was allowed to race on a dispensation that they build the car by the end of the year They didn t and ACO later banned the car The Panoz GTR raced in the old GT1 class alongside the Porsche 911 GT1 and the Mercedes CLK GTR but once again it failed production requirements and when it returned it had to race as a prototype The same could be applied to our situation when we have cars such as the Laraki Fulgura the Farboud GTS or the Bristol Fighter who are available for sale but fail to attract a number of customers or cars such as the Hispano Suiza HS21 or the Isotta Fraschinni T8 which are presented to public but only the show car is built or even the TVR Tuscan Speed 12 of which two street legal in rolling conditions prototypes were made these cars can not be considered standard road versions because there aren t enough cars running around to be considered standard And look at what Pagani did They had a 6 0L engine decide to increase to 7 0L didn t like it increased it again to 7 3L people complained of lack of power they increased power from 555 to 602hp That s four variants for less than 40 cars made