Mechanical keyboards have a reputation, and it is earned. People buy one to type more comfortably and end up owning five, plus a drawer of spare switches. The good news is that the first one does not need to be expensive, and knowing how the spending spiral works helps you stop at one.
A mechanical keyboard uses a separate switch under every key instead of a rubber dome sheet. That gives each key a consistent feel and a longer life, and it lets you choose how typing feels. Linear switches press smoothly straight down. Tactile switches have a bump you can feel. Clicky switches add a sound, which your coworkers will have opinions about.
The first choice to get right is layout. A full-size board has a number pad. A tenkeyless board drops it, and a 75 percent layout squeezes the arrows and function keys closer together. Smaller layouts leave more room for your mouse, which helps your shoulder. If you use a number pad daily, keep it.
The second choice is hot-swap sockets. A hot-swappable board lets you pull switches out and push new ones in without soldering. This is the feature that saves money, because if you dislike the switches you bought, you replace a set of switches rather than the whole keyboard. It is also the feature that starts the habit, so consider yourself warned.
Keycaps are the next temptation. PBT plastic keycaps hold up better and resist the shiny wear that cheaper ABS caps develop. Many mid-range boards now include PBT caps, so there is no need to buy a set on day one.
Programmable firmware such as QMK or VIA lets you remap keys and build layers, and it is worth having. Wireless, knobs, gasket mounts and aluminum cases are nice, but they are where the price climbs quickly.
The wallet problem comes from the hobby side: group buys for custom cases, limited keycap sets and switch testers. None of it is required to type well.
The short version: buy one hot-swappable board in the layout you actually use, with PBT keycaps and remappable firmware. Try its switches for a month before changing anything. If you still love typing on it, then feel free to start the drawer of spare switches.
