IMPORTANT: What would be a comfortable tournament entry fee / prize size?

We are currently trying to put together our first Tournament and have various ideas for what to have as prizes for the winner(s). Partially in an attempt to limit the tournament size to those truly committed to the competition and to compensate for the costs of putting the whole thing together, there will need to be a small entrance fee. The bigger the fee or the more people who enter, the bigger the prize; but we want to keep things reasonable too. Keep in mind, this event would easily run quite a while and depending on your level of skill and luck, would provide hours of entertainment, not to mention social networking, ect. I want to make this an event for you, the players, and need your input. The following are based on a tournament performed via the Xbox 360 console. Want a tourney for another platform? let me know!!! All fees and prizes are based on the assumption that promotion and venue could be obtained at little to no cost and may need to be changed accordingly.