Redesigning the article editing UI is pretty darn important when the only thing that ensures the site stays up to date is attracting new editors to work on it. Nobody wants a dead Wikipedia with hopelessly obsolete and misleading information, even though it would be incredibly cheap to host. And the Wikipedia partner projects are just as important as Wikipedia itself to the broader ecosystem of open content and open knowledge. Wikipedia needs its sister projects, and money spent on them is in no way "wasted".