Seems like everybody does this, except companies (which is probably why manufacturers still slap these high prices). It's ECC memory, though, I think it's more expensive than non-ECC (still not that expensive).
In academia — or at least in STEM and the social sciences — quite a lot of people need a somewhat high-spec machine (e.g. to run quantitative models on large data sets, compile code, process large LaTeX documents, etc).
And the basic model Macs generally come with woefully little RAM and rather small SSDs. So I'm not sure it's reasonable to be hacked off.