I grew up on machines chronically starved, think 16MB for Mac system 5-7, and 32MB for win98 :) (which leaked like a mofo, reboot required every 20 minutes.)
It's only a bargain if you need it. For a general purpose computer I'm with you, but the Pi5 often isn't used as a general purpose computer so if you know the software isn't going to be using it then it is pure waste.
Pi's aren't a great value for general purpose computing when cube-PCs will get you orders of magnitude more power and functionality for 2-4x the price, and people often neglect to factor in the price of a case, PSU, storage which stack up the cost rapidly.
Every generation I grab a couple of the latest model-B and run a few quick desktop tests to see where they're at subjectively (no benchmarks, just boot it up and "use" it) and Pi 5 is still orders of lower than what I expect from a computer.
Put them to work in a specific application and their reliability and great ubiquity shine; I have a couple of Pis in 3D printers, one powering a touch-screen dashboard, a couple in my server rack for Hashicorp Vault, Unifi Server, ARM build server, a half a dozen or so in home-made speaker/TTS devices, a couple in retro gaming-handhelds, one in a dedicated WiFi AP for MiTM/testing/traffic-inspection, and one with a NVMe HAT running a file-server for low-power network storage.
Each Pi serves a purpose, and I've allocated a device a specific model based on its requirements; a couple of them are probably over-powered just due to having a specific Pi spare, but I try to shuffle them around to be using the weakest/cheapest Pi available that suits the purpose.
... don't forget to add more cooling for that reliability
I don't see 3 Bs in stock in my usual places. 4s and 5s are plenty though.
Eh, not orders of magnitude more. An RP5 is like 25% of the speed of an Apple M3.
(Don't ask how I know it)
Once you are using a lot of paging, chances are performance has fallen through the floor to the point where doing anything to fix it (killing run-away processes, closing other processes (killing those that won't go willingly)) takes so long that you are fighting a losing battle. This is less of an issue with fast SD drives than it is with spinning rust (or slow SD cards / eMMC with some smaller devices) but still essentially the case.
I just have enough swap defined for some small unusual circumstances and assume that if I need more than that things are falling over anyway so OOM taking things our is not going to make it worse (if they continued to thrash I'd have to kill them anyway).
Ubuntu does this by default and has done since 18.04 or so, maybe earlier.