Pi5+ just because I'd originally written Pi5+PS/case/SD.

And you're right that everything has gotten more expensive, but $35 in 2016 (Pi-3) is only $45 today (and you can still get a 3B for $35). The older Pis hit, for me, a sweet spot of functionality, ease, and price. Price-wise, they were more comparable to an Arduino board than a PC. They had GPIOs like a microcontroller. They could run a full operating system, so easy to access, configure, and program, without having to deal with the added overhead of cross-compiling or directly programing a microcontroller. That generation of Pi was vastly overpowered for replacing an Arduino, so naturally people started running other services on them.

Pi 3 was barely functional as a desktop, and the Pi Foundation pushed them as a cheap platform to provide desktop computing and programming experience for poor populations. Pi4, and especially Pi5, dramatically improved desktop functionality at the cost of marginal price increases, at the same time as Intel was expanding its inexpensive, low-power options. So now, a high-end Pi5 is almost as good as a low-end x86, but also almost as expensive. It's no longer attractive to people who mostly want an easy path to embedded computing, and (I think) in developed countries, that was what drove Pi hype.

Pi Zero, at $15, is more attractive to those people who want a familiar interface to sensors and controllers, but they aren't powerful enough to run NAS, libreelec, pihole, and the like. Where "Rasperry Pi" used to be a melting pot for people making cool gadgets and cheap computing, they've now segmented their customer base into Pi-Zero for gadgets and Pi-400/Pi-5 for cheap computing.