I understand your question that what cars are available off the shelf. And the answer is all of the cars that the company can afford to keep stock of. But let me first explain why limited editions are made and why some supercars are sold out completely.
Buggati made the Veyron which was supposed to be the ultimate supercar of staggering numbers. But the cost of development and the cost of materials is so high that they cannot just make the car and keep it readily available in the showrooms for rich kids to walk-in and get one. What if the market is not willing to buy one. They wont risk having a million dollar supercar rusting away. And what if they even put it in the showrooms. People will say, "yeah, I like the car but let me wait for a friend of mine to take delivery, post an ownership review to me and then I will buy. It's not like the car will go anywhere".
To address all these troubles at the same time, they make them as "limited editions" and one of only 150 ever built. The response is overwhelmingly good and there are more potential owners maybe in 100's. So, they think, "good, there are more people. So, let me make some more. But I cannot call them the same because people will loose trust". So, they add a stripe, slightly bigger turbo and they call it as Buggati Veyron Supersport. And only 50 will ever be made (all numbers are figurative and do not denote the exact quantity).
Then buggatti earned more fame and more people wanted to put down their investment. So, they add forged pistons and better cooling system and re-designed head, make the body out of naked carbon fiber and they call it Buggatti Veyron Super Sport Grand Vitesse. And only 50 of them will eve be built. And 10 of them are sold. The remaining 40 are yet to be sold because Ferrari LaFerrari, McLaren P1, Porsche 918 have come to the scene and people cancelled the booking for their Buggatti. So now, Buggati is making the Chiron, in blunt terms a Buggatti Veyron facelift. Why. Because the accountants at Buggati realized that you just can't keep on making limited editions as if it were a continuous production. Buggatti lost exclusivity and people started thinking, "yeah, one model of the veyron or the other will always be there. So, never mind, I will buy when I feel like it".
Lesson learnt for every car maker and so Ferrari LaFerrari, Porsche 918 and McLaren P1 are limited editions. They wont make another of those models unless the demand is so high that the profits made out of it will justify the cost of sacrifice of exclusivity.
So, if you and 50 of your friends can get in touch with Ferrari and express interest in LaFerrari, there might be another edition called Ferrari LaFerrari Track edition. And only 25 will ever be built
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