Burnett was fortunate to perform exceptionally well during his contract year which proved to earn him more money and he was 32, not 36. How many 36 year olds get 5 year deals? lol. AJ finished the 2008 season with an 18–10 record and established career highs in almost every single pitching category. He set a career high with 18 wins, started 34 games, pitched 221 1/3 innings, and led the American league with 231 strikeouts.
The Yankees are already going to overpay Jeter, I'm sure they're willing to dish out a extra 2 million so he makes more then Burnett if it comes down to it. But the fact you think he should get a blank check from the Yankees is a bit absurd.