WSJ:
Since 2011, the NFL has had a rookie wage scale, which allocates relatively affordable salaries to each draft pick regardless of position. That means taking a rookie at one of the more valuable positions has the chance to generate enormous surplus value. It’s why, for instance, quarterbacks on rookie deals are so advantageous—teams can get the most from them before they re-sign on contracts that could cost upward of $50 million a year.In other words, quarterbacks salaries are fixed further below expected value than other positions, so they generate more expected profit for the team.