I'm typing on a 300 euro keyboard right now but I would consider it a gross waste of money if a company decided to give them to every single employee regardless of need or preference. For instance for most people better chairs and desks would be a vastly better investment, ergonomy-wise.

In both cases the stuff people are fussing over is basically a rounding error compared to the big factors.

Beyond some basic utility, e.g. being able to compile the code in under 5min, the hardware one uses is of negligible impact to their success. A developer will succeed or fail based on their training, mentorship, the nature of the tasks they are given, and all the other more social and interpersonal facets of the business they fine themselves in. A glitchy mouse won't make them or break them.