A rather expensive hobby I have managed to find for myself is building and modding mechanical keyboards. Much of my time is spent typing, whether for uni, programming, writing for the website, gaming, or just using a computer largely through a terminal. Having a keyboard that feels high quality and, notably, is tuned to personal preference, is rewarding and worthwhile to me.
Unfortunately the market is expensive and still largely operates on 'group buys' – a business practice where expressions of interest dictate which projects go ahead, and all orders are placed before any manufacturing begins. This makes sense for a small market, and is a very sustainable practice in general; Hank Green uses a similar model to control waste with his merch.
For keyboards, this is largely a relic of being much more niche than it is today. It worked when modded premium switches were made by one person with leftover commercial switches, but now that exposure and demand have increased it creates a culture of exclusivity that bloats prices and renders it inaccessible to newcomers, with large price tags and long lead times. Additionally, combining this with large amounts of money being prospectively placed in premium products from small, often young, companies risks turning sour in a way not entirely dissimilar to failed kickstarter campaigns or cryptocurrency rug pulls.
The flip side of this is being involved in a community that strictly cares about manufacturing what it legitimately wants, with a (generally) very low barrier between producers and consumers. Quality and attention to detail precede profit, and there is a tremendous sense of human passion here – something that feels increasingly rare with material (consumerist) hobbies.
All this to say it's a tenuous thing to become invested in, and requires more passive engagement and research than one might anticipate. It's very fun, very satisfying, very rewarding, and if you have the means and opportunity to build one then I thoroughly recommend it.
The Zoom65 was the first I built and consequently covers much of the preamble for the other articles. I recommend starting there!