(However, after buying a mech keyboard to deal with finger joint pain, and training myself to type without bottoming out much, I discovered I was typing faster.)

(1) Ensuring your chair, desk, and keyboard are set up so your wrists are straight when typing

(2) Using a split/tilted keyboard so your wrists do not need to rotate as much when you type

(3) Using a vertical mouse so your wrist does not need to rotate as much when mousing

You can accomplish all of this for very cheap. A bit more than you're spending, but not an order of magnitude more (unless your desk or chair are very bad). Once you get into mechanical keyswitches or exotic keyboard layouts you're just messing around imo. Membrane keyboards are fine. They're fine! And very quiet.

I've indulged in a nicer keyboard once before, but only because I was intrigued by the novelty of mechanical keycaps. Now I'm thinking that I'll need to take the plunge and get something more ergonomic, because I've still got a lot of career left.

I've had RSI issues in the past, but this spring (when I bought those two), I was in intense pain for days at a time, even when not at my desk. Otherwise good ergonomic setup: external monitor, adjustable desk and good chair, etc.

I'd suggest you at least take small steps to improve/optimize your ergonomics before you have a problem. It really does suck to be in pain like that, especially when doing your work, which you have to do to pay the bills, makes it worse. I was looking forward to weekends just for some relief.

For what it's worth, having a programmable keyboard is super cool even without the ergonomic benefits. It's just fun to tinker and optimize your layout, macros, etc.

I wish I cared more earlier. The injury in my left thumb may never go away fully, and it’s taken me a really long time to come to peace with that.