Yes, the DRAM dies all come from the same wafer supply and fab capacity, and those limits are the cause of the current prices. However, once the memory OEMs have packaged DRAM dies into something like an LRDIMM or SOCAMM, the cake is baked. It's no longer usable in a laptop or desktop. No amount of X-year-old LRDIMMs (hypothetically) flooding the market will be useful for anyone's desktop or laptop. And then there's HBM, where the dies are directly on-package with the CPU or GPU.

Second-hand, revalidated server DRAM components may contribute somewhat to a price decrease, but those won't be the components you or I will be purchasing (unless you run a true server platform as a desktop, in which case, shine on you crazy diamond!).

The same is partly true for GPUs: there are PCIe versions, but most are OAM or SXM modules. You might be able to jury-rig an SXM module into a desktop? Adapter cards exist for at least some SXM versions, and you could figure out the cooling somehow? But it's probably more trouble than it's worth.