Like Elvis said, it depends on what your goals are.
For example a brick-and-mortar small business trying to increase their conversion rate with a 1 minute promotional video can expect to pay around $500 for a "TurnHere" quality video. Corporate videos made by professional videographers can run into the thousands.
For affiliates, some companies supply videos to their affiliates.
In my opinion, you're far better off to have no video on your site than a poor quality video. So either make a really good video or grab one off Youtube.