Out of interest I just dug out my invoice for the pi500+ I brought almost exactly 12 months ago - looks I got it at around 40% of the price it goes for today.
I agree with the other poster though, ESP32 is a good alternative if you don't need linux - these things are great ...
https://shop.m5stack.com/products/atom-lite-esp32-developmen...
People don't sell enough of them, so the supply/demand curve favors demand and the price is only tempered by that of new hardware (if it is available).
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I have a theory for this:
Lots of folks buy Pi hardware. And by that, I mean: It's small compared to the market for iPhones, but it's enormous for a quirky SBC with DIY traits. But lots of those folks futz around with them and lose interest. Into the drawer they go.
People assume the value of computer-ish electronics drops over time. And most of the history of personal computers, that's broadly been very true.
Plenty of folks sell stuff on eBay, and those who have done so know that it can be a pain in the ass to deal with. Packaging, descriptions, printing, photos, getting the thing to the post office or whatever, dealing with the risk of getting ripped off: It sucks. It especially sucks for small quantities of unique (to the seller) low-value items.
So that Raspberry Pi (whether once $20, $40, $80, or whatever) sits in the drawer. They might sell for $200 today, but the uninterested owner doesn't know that. They assume that it's worth less than the cost of a pizza and just isn't worth fucking with at all.
So, even if they might be motivated to deal with eBay for a couple of hundred bucks, their lack of interest means that never know that the price is high.
Accordingly, the devices stay in the drawer. Maybe they'll get binned after a few more years of taking up space.
This includes all of that