It is called the auto industry. They can predict fairly well how many luxury cars can be sold. I forgot the exact math, so for every X K price increase demand drops Y%. Elon knows damn well the true demand for the M3 at each price level. I would say half of the people signed up for it thought they can buy it for 35K or even with the tax credit. The tax credit will be minimal by the end of this year, and there is no basic M3 for 35K. Thus the claimed demand can be easily cut in half.
Anyhow there are other data available if you read SA...
https://seekingalpha.com/article/4176298-tesla-finally-sees-good-news-things
"Elon also confirmed that a great majority of deposit holders are waiting for the bare-bones $35k version rather than buying the loaded version like bulls claimed they would."