With the Nvidia RTX 3090 launch a mere few hours away, Nvidia has advised potential buyers to expect a shortage of cards much as was experienced with the recent launch of the RTX 3080 cards. The company has issued a statement already apologizing in advance for shortage.
https://www.notebookcheck.net/Nvidia-warns-low-stock-of-impending-RTX-3090-launch-GPUs-expect-more-customer-blowback.495204.0.html