They spent the money on stuff that mattered more.
Stuff like the Rura Penthe scenes that got cut completely.
Guess what - scenes that were part of the narrative were more important to get on film than the color of the wallpaper in engineering was - yep, even if they were eliminated from the final cut.
Do you know a thing about writing and editing films?
I would have rather had the Rura Penthe scenes--which gave us some back-story to go along with Nero and fleshed him out a little more--over the Benny Hill moment in "engineering" we got later.
Besides if they didn't have the moment to do a engineering set, why not just leave the set out all together and have the chase scene somewhere else on the ship.