So Hollywood can generate realistic looking footage of 50 foot high humanoid robots fighting each other in downtown Hong Kong, but it can't digitally correct some orange dollar bills to make them appear green?
The movies with giant robots tend to have vastly higher budgets than the ones involving suitcases of money, although these days 'invisible' FX are the norm even on lower budget projects.
But I think it's more to do with departmental splits. ie if you're the prop guy and you turn up with a pile of orange money saying 'just CG it' then you're offloading part of your job onto a different department and messing up their budget, which is a big no-no. Producers always prefer the person who makes things simpler over the person who makes them more complicated.
Bear in mind that the majority of people work together on a per-project basis so organizationally film production is more fragmented than you might expect. Even on big productions you typically don't know many of the people you are working with at the start of a project and you only meet each other a few days or weeks before shooting starts. Like any other organization, different departments guard their budget allocations jealously.
When I had seen 50 foot humanoid robots on film they were everything but realistic, also the fact that you don't know how a 50 foot robot really behaves helps a lot. Normally they hide the problems using light, making it dark, like a night scene.
Making video realistic with bright light is really really hard and really really expensive because in the real world there is dust and rust, and dirty mud and imperfections everywhere, but those are hard to model.
Even then most film professionals will know instantly is something is created digitally. It is exponentially more expensive to improve in this area, so they compromise on what most people would consider ok for the least price.
Even super expensive productions like Starwars look very artificial for the trained eye.
Is it really cheaper to hire CGI artists to recolor stray bills in every frame rather than to hire two security guards to guard and re-count a pile of real cash?
Sure, handling piles of real cash is a bit tricky - but it's a well-practiced routine that is a cheap&efficient commodity, since so many businesses need it for their everyday operations.
