What's a franchise tag worth for Vick?

If you've studied your franchise tag rules, you know that Peyton Manning will make more money in 2011 than Michael Vick. ESPN.com's John "The Professor" Clayton, a national treasure, hit on this topic in his most recent mailbag column:

Question for The Professor from Josh in Washington D.C.: Can you please explain the difference in franchise tag salaries between Peyton Manning ($23 million) and Michael Vick ($16 million). How/why can the top-five average salaries benefit Manning more than Vick?

The Professor himself: Very simple. Under the franchise tag, a player gets 120 percent of his previous season cap number or the average of the top-five cap numbers from the previous year, whichever is greater. Manning had a cap number in the $19 million range. The 120 percent increase took him to $23 million. Vick got the top-five average, which was $16 million.