A sizable percentage of all of the Pi devices made likely are sitting unused in boxes in closets around the world. The resale value isn't high enough to motivate many people to go find them and sell them to those who would put them into productive use.

https://rpilocator.com/ (there are twitter and telegram bots to provide alerts)

I managed to get one from Adafruit last week. They restock ~weekly, typically Wednesdays, and sell out within a few minutes of the notification going out.

I don't get how they can sell out so quickly. Why won't stores simply raise the price in order to reach parity between supply and demand?

The official suppliers are required to sell at MSRP. People buy and then resell at higher prices so you can usually find them on amazon and eBay for double or more the MSRP.

... because they're not douchebags?

Supply and demand balancing doesn't make you a douchebag.

Because the Raspberry Pi Foundation typically negotiates agreements with its resellers stating that they won't sell above MSRP.

Good alternative is getting used Chromeboxes or Intel NUCs on eBay for $30-ish each.

Yeah and even an outdated atom box with a decent SSD way outperforms a pi when running something like Home Assistant. While using about the same power (5W or so).

It's a much better option if you don't need the GPIOs that the pi offers (I do so I do use one, but with an SSD over USB)

What are good models to search for? I think my rpi or SD card just bit the dust, so looking for a new mini home server.

Take a look at https://mrchromebox.tech, particularly the "Supported Devices" page for models that can be upgraded to a firmware allowing the install of other OSes. Chromeboxes and Chromebooks by default prevent the user from installing and running anything except ChromeOS, which is a lot less powerful than Linux and others, but thankfully that limitation can be worked around. I've repurposed a good number of them, mainly Asus and HP ones, by following the instructions at that site, and never encountered any problems.

I also have all my Raspberries collecting dust after I swapped the last working one running Kodi with a Asus CN62 Chromebox: the performance difference is huge.

It depends also on whether you need a real name brand Raspberry Pi or whether you can use any equivalent computer. For instance, pine64 makes significantly nicer hardware in the same price range and is actually in stock.

I'd pay Pine64 50% markup if they'd just deliver to my damn country.

Every now and them, I check their store, just itching to buys stuff and build on top, but no delivery for me.

Any other similarly supported/open alternatives you'd recommend?

At the https://www.raspberrypi.com/raspberry-pi-store/ in Cambridge UK :)

I bought a raspberry pi 4 in Canada from pishop.ca a few weeks ago

I was surprised to find pi's are going for > $100 on amazon.

I think the nuc-like boxes might be competitive, but I wonder if they aren't inflated too.

ebay?