In an article on Gamasutra, game developer and president of Game Mechanics John Ardussi claims that 150,000 views of a YouTube video featuring a game only generates about 10 game sales.
Ardussi did not detail how he came to this conclusion, and not all games have that kind of sales performance as it relates to YouTube exposure. In other words, mileage may vary.
But Ardussi still has doubts that YouTube exposure generally stimulates sales in any significant way.
"There is a huge difference between getting the word out and sales," he notes in his article on Gamasutra.
Ultimately the point of Ardussi's article is that YouTube personalities need to do a better job of helping game developers by giving out as much information about the games they are reviewing as they can.
"If you are a [YouTube] reviewer, get better at helping the developer. You don't have to change your review of the game, just make sure you give out all the information needed."
You can check out this fascinating article on Gamasutra.