When I studied computer science the VAX-750 had 4 MB and 15 students could compile at the same time from each their terminal. Swapping got a bit annoying under those conditions, but in the evening when a couple of them had gone home it started to run smoothly.

I remember phones from 20 years ago using something like 150 kB, admittedly they had no real operating system, just a simple task scheduler. Probably color display required a bit more already.