Is there any real technical reason to have soldered RAM and storage ? A well built $1200 linux laptop would still be OK if it weren't artificially gimped. M.2 ssds are already quite thin. So the form factor argument doesn't hold. The storage markup on these devices is huge considering that a 1 TB nvme pcie m.2 ssd goes for under $350 (even less during sales).
Looks like you answered your own question..