Not value produced, but easily quantifiable value produced, I would say. There are lots of cases where some perfectly tweaked internal tool saves hours of work

Not value produced, but easily quantifiable value produced, I would say. There are lots of cases where some perfectly tweaked internal tool saves hours of work every week, or some mostly invisible (but crucial) project, application, or module just somehow always works. But the user never twigs they exist, and the customer doesn't care. The value is there (in saved hours, frustration, and stability), but it won't count.