There are no "odds". The game has already determined what you're going to win before the roulette even starts. They throw in absurd cars to provide incentive. @Famine, and other users including myself, have already experimented in a previous thread on the GTS forums regarding this very issue.
Like you said, a one car reveal would be a lot more ethical and aesthetically pleasing than the current slap to the face.
Then how's it possible for some people to never have won a 10 15 or 20kk car and others have won several?
Iven if it's predetermined, there are different results for different players and the odds I got a really bad chain of prizes is real. In my view, my odds are atrocious.
And if PD chose to give me a determined chain of prize cars that after hundreds of logins, daily rewards, events, etc I never won an exotic car, they decided I should never be able to get them. Because the credits I've made were only enough to buy the 15mil Cobra and then all the race cars I needed and wanted. It's not possible to buy exotics with micro transactions.