Prices
Top perspective - cards use same 3D NAND and similar controllers to SATA drives (usually they try to make more channels or use TLC in MLS mode).
And 120GB SSD with same speed sells for $23-28.
Let's assume worst case - that they run TLC memory in SLC only mode, this produces retail cost around $70 (as it is 3x RAM chips) for 120GB drive.
I am sure they do not use such approach, as it is cheaper to increase channels or run memory in MLC mode.
Sources tell that single slot and XQD one was among top Sony demands to for Nikon to get their sensors.
Sony will also get good share of all Nikon profits from cards via unusual sharing scheme.
How this look inside
Standard SSD controllers and standard NAND chips.
This is now outdated: the latest firmware for the Nikon Z 6 and Z7 enables use as well of CFExpress cards in the same slot. These are also expensive, but I do not see the Sony connection. "CFexpress is a standard for removable media cards proposed by the CompactFlash Association." Wikipedia. So there can be competition, and indeed SanDisk makes them.
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