Among other things, I'm a recreational bicyclist, and as this I'm a fan of basic wired cycling computers, which in their own way are fascinating artifacts. A wired cycling computer is a little electronic device with an LCD display that shows you things like your current speed, how far you've come on this trip, the time, and so on (generally not all at once; typically there are several screens and you switch between them with a button). A wired bike computer gets all of this from an internal timer and a simple sensor to track wheel revolutions; this sensor is basically a reed switch mounted on your bicycle's front fork, and closed by a magnet you stick on a spoke of your front wheel. When the magnet goes past the reed switch, the circuit closes and the bike computer gets a pulse, which it counts (and wakes it from idle if it was idle). The whole mechanism is so simple and straightforward (and reliable) that I've always loved it, and the whole thing is sufficiently power efficient to run for years from a single coin cell.

(The cycle computer goes from wheel RPM to speed by having you tell it your wheel's size, through a setup process that also sets the current time.)

For a time in the 00s and 10s, capable basic wired bike computers were readily available from many places for not very much money, which I found impressive. Here was a moderately complex computing device, capable of math, storing data (bike computers generally keep an odometer), displaying things, and handling a simple UI, and all this was cheap enough to sell to you for prices such as $30 Canadian. It was a real demonstration of how cheap basic computing had become.

Today, if you go looking around your local bicycle retailer or favorite online outlet, you'll probably find much less selection and rather higher prices (and what's left is often much more basic than before). This isn't necessarily because the basic components of a bike computer have gotten more expensive; if anything, tiny low powered computers have gotten even cheaper. Instead, it's probably because these basic bike computers have gotten much less popular. Today, most people who're interested in this sort of information use either their phones or a GPS based bike computer (which doesn't even need a sensor, although it does need a GPS signal).

The lesson I draw here is that the cheap price and wide availability of these basic bike computers didn't come just from that their components (the simple computer internals and the basic LCD screen) had become inexpensive. That the components were inexpensive was simply a necessary prerequisite. What drove the finished units to be cheap was that they were popular and sold in volume. When they stopped being popular and the volume shrunk a lot, the price went up even though I rather suspect that the components are no less inexpensive than they used to be, or would be in large enough volume.

Application of this idea to aspects of computing, servers, and so on that I now take for granted are left as an exercise for the nervous. Are SATA SSDs safe, or will someday everything be NVMe? Hopefully USB-A connectors and USB 2.0 are safe, because we sure do have a lot of devices that really want that and I hope to be using some of them for decades to come.

(This is related to but not quite the same as how some computing things seem to have a floor price and what you get for that floor price keeps rising; disk drives are one example of this.)

(I'm currently thinking about wired bike computers for reasons.)