The original pis were made to sell some chips that Broadcom had a ton of excess inventory for, and needed to move (hence why the price was so low compared to other SBCs at the time - the main SoCs were free). The modern version is now competing for a chip that's in demand, and can't offer the same price that other people can. They are still being produced since Broadcom doesn't want to cut them off completely, but not nearly as available.