[OJFord]

If it's helping the job then we ought to (be able to) expense it, there's a much higher bar for getting me to pay personally to help my work - as in it can't just be 'do it faster' (at the end of the day, do/should I care?) it would need to be posture/eye strain improving and not offered by employer, or something like that.

Imagine an embedded engineer personally buying a higher bandwidth 'scope (or whatever) to better debug an issue or QA before release. I don't doubt it happens, but I think it's more clearly unreasonable, and I don't think theres any reason it makes more sense with software.

Especially since software might well have per-device licencing, so you put it on your work machine and then what?

('I have better kit at home, I'm taking the DUT home for the weekend' is still overworking, but probably a lot more common, and I don't think quite the same/as bad as personal spend motivated by work.)

Regarding 'developers are cheap' directly, in my (limited, but spanning large & very small/growing company) experience businesses are cheap: they multiply the per-seat cost by head count and run scared, overlooking completely that it's a rounding error on payroll, or that it's more than covered by the unpaid salaries of open positions that might've been filled. (Obviously there are boring reasons this can be that you don't need to reply to me about. So too are there myriad reasons not to buy something personally beyond being 'cheap'.)