CAMM, unlike DIMM, is designed to be amenable to stacking from the get go.

A single LPCAMM2 module is supposed to be all the RAM for a laptop, so it’s 128 bit wide. You’d need two LPCAMM for this, not four. And they are currently available in 32G and 64G varieties ($180/$330). So they aren’t absurdly priced, if they were in stock.

For dual channel 256-bit wide LPDDR5X, you would definitely need 4 CAMM modules

It’s also not that absurd pricing of the modules themselves but of the R&D effort to cram 4 CAMMs onto a board with sufficient signal integrity

“Dual channel” is not a thing with CAMM. CAMM is 128 bits wide. To feed a 256bit wide memory controller, you need 2 CAMM modules. LPCAMM2 uses 4 memory packages. The observed number of packages next to the APU on this is 8. So you need 2 modules.