This is not a "how long is a piece of string" question. It can and must be quantified and measurable.

The budget should always relate to the value that the objective of the production is set to achieve: (If people watch this video they are better informed and will save the organisation x amount of dollars). If the staff don’t do what we show on the video, we are liable to lose x dollars? I can achieve the objective by another means for y dollars.

Your budget must be a function of X dollars. For example if you are losing Millions of dollars in Fraud …spending $30,000 on a video that increases compliance from 20 to 75% is worth it.

Conversely, if a message to the interstate branch is delivered by the MD on tape instead of actually traveling himself to deliver it, then the video style and budget should reflect the opportunity cost of travel and the MDs time.