How do you calculate the time spent on an internal tool like this, actually? (I’ve never been in management). Realistically your team inevitably will have some downtime, maybe some internal tool maintenance can be fit in there? I mean it obviously isn’t fully “free” but is also shouldn’t be “billed” at their full salary, right?
What? My team wouldn't have any downtime even if we had 10x the amount of people.
If you work at a company where you have times where you don't have work to do, you should polish your resume because it means the company will go under.
I think most software companies need to be doing less. Deleting code, refining, and making their product genuinely useful as opposed to "able to technically contort to client needs".
In broad strokes there's two ways. You can count it as an operational expense, or you can count it as capital (this takes more work to do but can have some advantages). If you count it as operations, it's just a big red pit you're throwing money into that you hope is offsetting a larger operational cost somewhere (but this can be hard to quantify). If you count it as capital, you're basically storing all of those hours as an "asset" which then loses value over time (it's kind of like the charge in a battery). The problem is you have to be able to show that this internal tool would, in the case of an acquisition or liquidation, be valued by the new owner at the value you're setting it at.
The problem there being that people are even more hesitant to trust somebody else's internal tool than they are to trust their own internal tool, so I've seen multiple managers think "I sunk a million dollars into this so it must be worth something" but in fact they were just running a jobs program for their team.