Actually he was the #1 CF'er on the market and was worth, at the time of his signing, around $24m AAV due to his prior performance. We may have paid more than other teams offered, but considering his age, AAV and prior numbers , nobody who follows this stuff closely was alarmed by the deal. It looked like a pretty good deal at the time especially since he had yet to turn 30. I think some of this criticism is revisionist history. How was any GM to know he would fall off the map like that? Lately he seems to have righted the ship, and maybe that's because playing with his brother messed him up, or the team messed him up or Fredi sucks as a manager...etc Yes Bj underperformed (and that's putting it mildly) but, AT THE TIME IT WAS SIGNED, there is no way it was a bad deal.
edited to add: between 2007-2012 seasons (his 6 with the Rays) BJ was tied as the 4th most valuable CF'er in baseball amd 30th overall, that's a top tier guy
His last two seasons in Tampa are more indicative of his actual value. He was essentially a 3 WAR player but had declining on base skills. He wasn't terrible, but be certainly got paid more than he was projected. And I'd argue that Bourn was more valuable at the time, being that he was coming off a 6 WAR season.