They are available in that quantity. They do make sense up to around that number, although the around 1K is the sweet spot. Laying out and certifying a high speed design (not just a noddy A9 with DDR2) is expensive and it's all NRE cost. The cost of the components for the CM is driven down by the combined volume significantly - if you want to buy 1-10K of those by yourself, you will pay a premium over what RasPi gets them for. You might not need a full 6/8 layer board for the whole product as well. As important, the software support is great as it's just a standard RasPi - you don't have to support your own custom image.

They are far from the most expensive SOMs on the market.

Volume pricing on custom commercial Pi SoM are not common, but do happen at the Pi foundation.

I have seen 3 or 4 products with these pi+Debian SoMs running network services etc. Getting them to be reliable is a different set of issues with dozens of edge cases, but its the same with every other vendor. Best regards =3

There are apparently products based on the CM (Ableton Move?), not sure how they sell these at a profit.

Mass producers do not buy at retail prices.