As you mention on your blog post, SBCs (especially good ones like the Rock Pi 4) get used in all kinds of small volume products as well as by the makers for whom they were originally intended.
The RPi form factor is a smart choice to gain an instant large ecosystem, but can be limiting for products/projects, particularly with ‘PC style’ connectors on two edges at right angles rather than one.
I think this was as big a contributor as the price to the runaway success of the RPi 0 and 0w boards, where demand outstripped supply for a long time despite a seriously underpowered armv6 CPU and 512MB RAM. Similarly for the RPi compute modules, although for one-off/maker projects, those are perhaps a little bit too ‘bare-bones’.
There’s a nice gap in the market IMHO for something between the current Rock Pi 4B and the various ARMv8 compute modules, a Rock Pi model C (say). Personally, I would include the wireless module and all the hardware that’s on the model B board, but just bring out the lines to edge fingers or headers instead of the USB, HDMI, ethernet, etc. jacks. That makes it very easy for makers to integrate into projects, but also flexible enough for professional users.
Of course, replacing the ‘conventional’ connectors would also make it easier to bring out all the MIPI lines, more GPIO, etc.
Without the connectors, it should be cheaper to manufacture, but I don’t think it would need to be at a lower price to the existing 4B board: the ease of ‘deeper embedding’ it in a project/product is the sales pitch rather than the price per se.