I worked in the period between 1970 and 1992 and have always maintained that I only got paid big fees to produce a result (to the client's brief) that did not already yet exist. Once it existed, whether film, video, or still photograph it was worth very little in the marketplace. I made my money making client's perceptions (whether accurate or not) become reality as an image.
I once did a shoot for Coca Cola (Agency: Harrison McCann) in the Seychelles on spec. They agreed to pay me if they used the pictures in an advertising campaign. Two years after shooting I saw the posters with my pictures go up all over Britain. They offered me a derisory amount so I took legal steps. I lost a lot of money to lawyers as well and got peanuts for my efforts. That was way back in 1985. Get the contract signed before you commit.
The last underwater video I shot (30 minutes) had a post-production budget of £10,000 sterling. It was in 1991 before you could get broadcast quality on your home computer. Even then we were offered around only £200 per minute to put it on mainstream TV.