Puzzle me this!: GeekDad Puzzle of the Week: The Present Game

Puzzle me this!: GeekDad Puzzle of the Week: The Present Game:

Imagine a row of seven presents. Their values are $1, $2, $3, $4, $5, $6 and $40. You don't know what's inside and so don't know which present matches each value. It costs $7 to pick a present at random. ...