All major camera brands as well as few cards manufacturers formed secret cartel to hold prices on CFexpress cards.

Such cards inside represent absolutely standard NAND chips from 2-3 major manufacturers and quite cheap standard controllers (can find on many M2 SSDs). So cost to manufacture for such cards is usually same or slightly higher compared to usual SSD, but retail price is very different.

Note that for some cards that offer top speed manufacturers also use mass market cheap 3D TLC NAND chips, but run it in MLC mode, it adds to manufacturing cost only slightly (around 20%).

Note that all manufacturers do everything to not make new SD cards working with PCIe NVME protocol.

Actually it has very simple reason. Offering such cards means that profits will fall significantly.

As controllers for them needs to be custom made, more energy efficient, also you need different, more expensive custom packed NAND chips.