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).