I spent a few years at Apple writing internal tools.

IMHO, this is the way to have an effect on a company completely disproportionate to any other activity I know of. The tools I wrote at Apple have enabled projects which, AFAIK, are completely unheard-of at any other tech company.

That said, don't expect a payoff proportionate to the effect of the tool.

From a company owner's perspective, however, excellent tools can provide an advantage that is difficult for competitors to match. That's worth an awful lot.