Experimentation
Opportunity cost
The value of the best alternative you give up when you choose something. Engineering time spent on internal tools is time not spent on the product.
Opportunity cost is invisible in a budget but decisive in a strategy. A team that spends six months building an in-house tool has also spent six months not building features customers would pay for.
It applies to design capacity too: every hour given to one activity is an hour not given to another, which is why capacity planning is about trade-offs, not totals.