Well... yeah, but they weren't all road cars. In fact only 62 were (plus the 5 prototypes, of which XP3 and XP4 were sold on and XP5 is retained by McLaren; XP1 and XP2 were destroyed), so you only really need another 31.
28 were F1 GTR race cars (18 regular, 10 longtail), and the remaining 11 cars aren't represented in GT7.
You could probably sort-of fudge the six (five plus XP1LM prototype) F1 LMs from either the road car or probably better off as the original race car, and the two HDK cars similarly, and make the three (two plus XPGT prototype) F1 GT from the longtail race car. Which will save you about 58m compared to just buying 106 road cars.