Ah, some context -- I live in Vietnam. We don't get tools or books from the 70's and 80s from the trash. New Chinese stuff is pretty good and not a fortune, although at the start I really couldn't afford even that. I was making like 240 US dollars a month in those days, and working 60 hours a week, so I had no free time to do labor-intensive things (or pursue hobbies at all, really). That's why I wanted tools so much I suppose : to do fewer labor intensive things so I could use my mind more.

AVRs are my favorite chips! I use the Attiny10 all the time (USD 0.36 per chip). AVRs have really nice assembly language and datasheets, they are a joy to work with! Attiny10 is maybe a bit difficult to do with the sharpie method. I bet you could with some practice and a very fine pen though.

I etch PCBs by hand at home sometimes these days, because I almost exclusively use SMT. I can usually do a board start to finish in 45 minutes, for iterating rapidly a few times before being satisfied with it. Toner transfer works really well on a gas stove + a big metal plate! However, I can also get boards made at a factory for 15-20$ with a 3 week lead time. That's usually much cheaper than a few 45 minute runs, so recently I've just been sending it off to the factory without etching + testing first.

The main cost is time, overall. I'm not wealthy, time is still super expensive to me right now, I'm in the finishing steps of bootstrapping myself out of poverty. An engineering company was a tool to monetize my interests, so that I could pursue a middle class life, without giving up the control I insist on having over my time and work. Really, it was the only way I could have pursued all this tech stuff at all.

Actual physical tools to do more work faster and more reliably was also really important. Having a company also gives me a 30% discount on tools -- no 10% VAT, and no 20% corporate income tax on the amount of profits it ate up (only if I'm legitimately using it for client work though).

Anyway that's a little slice of my life :)

Yeah, I've tried that! It was more of a journey making my work more presentable, than it was making it more functional, if we're being honest.

I invested some proceeds from an early client work to buy an SLA printer. It uses acrylic, with good dimensional accuracy, but it's very brittle. It was a painful expense at the time, nearly 800$.

I considered it a marketing cost -- I can't present things to clients with wires hanging out. Prototypes have to look awesome. I also sometimes use it to print basic clockwork, board game pieces, whatever I might personally consider fun. Mostly client cases though. I've had very good success with black plastic, which I polish down to a very smooth matte finish using fine emery paper soaked in water. I also emboss the client's logo on the case. I rarely paint it, but do sometimes add labels.

Another good investment was a decent used DSLR (135$) and some antique lenses (because they were very cheap and better than midrange modern ones). When I deliver physical prototypes, I also deliver product shots good enough to use professionally e.g. for marketing or to show the CEO / investors. A high-end ancient macro lens cost me 10$ and has paid itself off many times.

Finally, I also bought a rugged waterproof plastic suitcase filled with foam. Similar to a "pelican case". These are used to deliver prototypes to meetings and demonstrations.

I would classify this as 'theater' more than 'technology' -- but generally the management understands the former better, and they are the ones making purchasing decisions. So I give them a show, and the detailed documentation goes to the engineers only.

For my own stuff, I design it to fit in standard engineering enclosures. One of the local retailers has a quite good selection of aluminium and ABS ones. This is much more robust than any form of 3D printing I have access to (and it's cheap -- a nice ABS box starts at like USD 0.50). FDM printing would be OK, but I don't have the budget or space (actually space is the expensive thing in Asia) for a second printer.

The other thing I like doing for my own stuff is using solid and thick brass sheets, for no reason at all. Family ancestral shrines use a lot of brass here, so it's less expensive here. It's heavy, and chromed industrial buttons on brass panels looks glorious. Makes for great robots too. At least when I have an extra 15$ to spend (I'm quite stingy -- being poor in the past will do that to you).